bluuebunny/crossref_metadata_2025 huggingface dataset:
Location of stretch receptors in the trachea and bronchi of the dog.
Authors: Bartlett D , Jeffery P , Sant'ambrogio G , Wise J C
Published: December 2014

1. Using single fibre vagal afferent recording techniques, we have investigated the longitudinal and circumferential location of slowly adapting stretch receptors in a functionally isolated, in situ segment of the trachea in dogs. 2. We have also studied the depth of these receptors within the airway wall and their response to reflex and drug induced contraction of the airway smooth muscle. 3. Thirty‐four per cent of the receptors studied were in the extrathoracic trachea; calculations indicate that about 17‐1% of all airway stretch receptors lie outside the thorax. 4. All the receptors were located in the membranous posterior wall of the trachea, and those tested responded more to transverse than to longitudinal stretching of the wall. 5. Receptors in the extrathoracic trachea continued to function after the regional mucosa had been widely resected; subsequent removal of histolocially proven smooth muscle tissue caused the abrupt cessation of receptor discharge. 6. Contraction of airway smooth muscle brought about an increase in receptor discharge frequency. 7. Similar results were found for a smaller number of stretch receptors located in the mainstem and lobar bronchi. 8. These findings procided evidence that stretch receptors are anatomically located within the smooth muscle layer of the airways and are functionally aranged in series with the muscle fibres.
Adverse effects of tris hydrochloride, a commonly used buffer in physiological media.
Authors: Gillespie J S , McKnight A T
Published: December 2014

1. Tris 10mM, produced inhibition of motor responses to adrenergic motor nerve stimulation in all smooth muscles studied (rat anococcygeus and vas deferens perfused rabbit ear artery). Up to 30 mM Tris was without significant effect on those motor responses to cholinergic nerve stimulation examined (guinea‐pig ileum). 2. a similar reduction in responses to endogenous motor agonists was seen only in the anococcygeus, while in the rabbit ear artery, responses to noradrenaline (NA) were potentiated. 3. tris consistently produced increased tone in the rat anococcygeus and rabbit aorta, but in no other tissue, Small reductions in tone were seen with Tris in spiral strips of rabbit ear artery. 4. inhibitory responses to adrenergic nerve stimulation and to NA in the rabbit jejunum and to inhibitory nerve stimulation in the rat anococcygeus were unaffected by Tris. 5. in the perfused rabbit heart Tris produced a negative inotropic effect and reduced responses to vagal stimulation. Responses to sympathetic nerve stimulation and to ACh and NA were not significantly altered. 6. up to 40 mM Tris had little effect on responses of the rat diaphragm to motor nerve stimulation. 7. the effects of Tris on the rat anococcygeus were not reduced by increased calcium levels but were reduced at lower incubation temperatures. The negative inotropic effect of Tris on the rabbit heart was also reduced at lower temperatures. 8. the buffer HEPES produced a reduction in responses to stimulation in the rat anococcygeus and vas deferens along, but at higher concentrations than those of Tris. Increases in tone in the anococcygeus and aorta were never seen with HEPES. 9. These results indicate that Tris in concentrations commonly used as a buffer in physiological salines can exert toxic effects on neuro‐muscular transmission in smooth and cardiac muscle though not in skeletal muscle. The effects are variable, mainly presynaptic and appear to affect in particular motor and especially adrenergic transmission. They may be associated with intracellular metabolic actions of Tris.
Effects of antrectomy or porta‐caval shunting on the histamine‐storing endocrine‐like cells in oxyntic mucosa of rat stomach. A fluorescence histochemical, electron microscopic and chemical study.
Authors: Häkanson R , Larsson L I , Liedberg G , Oscarson J , Sundler F , Vang J
Published: December 2014

1. The argyrophil (enterochromaffin‐like) cells in the oxyntic gland area of the rat stomach contain histamine, which can be demonstrated fluorescence microscopically after exposure to gaseous OPT. After administration of L‐dopa (or L‐5‐hydroxytryptophan), these cells produce and temporarily store dopamine (or 5‐hydroxytryptamine), demonstrable by its characteristic formaldehyde‐induced fluorescence. Ultrastructurally, the enterochromaffin‐like cells, which have the appearance of polypeptide hormone‐secreting cells, comprise two main cell types, the most predominant one having vesicular type granules (EGL cells), the second most predominant one having smaller, uniformly electron dense granules (A‐like cells). 2. Rats were subjected to the following surgical treatments: antrectomy; porta‐caval shunting; antrectomy+porta‐caval shunting; or sham‐operation. Three to eight weeks after surgery the histamine‐storing cells (enterochromaffin‐like cells) of the oxyntic mucosa were analysed by fluorescence histochemistry, light and (quantitative) electron microscopy, and fluorometric determination of amines. 3. After antrectomy, fluorescence histochemistry and silver staining revealed a reduced number of enterochromaffin‐like cells. The histamine content in the oxyntic mucosa was reduced by about 50%. As in unoperated injection of pentagastrin seemed to mobilize histamine. Feeding or injection of insulin failed to do so in antrectomized as opposed to control rats. Ultrastructurally, the cytoplasmic granules of both endocrine‐like cell types were less numerous than in the unoperated rats. The reduction in cell number and granularity was particularly conspicuous with regard to the EGL cells. 4. After porta‐caval shunting the number of enterochromaffin‐like cells increased markedly. Chemical determination revealed a twofold increase in the histamine concentration of the oxyntic mucosa. Feeding or injection of insulin or pentagastrin lowered the histamine concentration. As judged by electron microscopy, the proliferation of endocrine‐like cells induced by porta‐caval shunting was restricted to the ECL cell type. Besides occurring in greater number, these cells were larger than those in unoperated controls, and their cytoplasm was densely packed with granules that were increased in size. 5. Following antrectomy of the porta‐caval shunted rats the number of enterochromaffin‐like cells and the oxyntic histamine concentration was reduced. 6. The results support the idea that gastrin exerts trophic as well as excitatory effects on oxyntic endocrine‐like cells.
Energetics of isovolumic contractions of the isolated rabbit heart.
Authors: Coulson R L
Published: December 2014

1. In the isolated beating rabbit heart the heat production (measured by Dewar‐flask calorimetry) and oxygen consumption (measured polarographically) increased in a similar way to force development (assessed as the time integral of left ventricular developed pressure) when the diastolic size of the heart was increased. 2. The energy expenditure of the heart consists of an element which is independent of the force developed and another which varies with the force developed. 3. The calorific equivalent of oxygen in the beating heart when it was provided with pyruvate as a substrate was found to be 20‐48 mJ/mul: O2 at 25 degrees C. 4. The anaerobic metabolism was well below 5% of the total energy liberation and was constant at all levels of mechanical activity.
Reduction in acetylcholine sensitivity of axotomized ciliary ganglion cells.
Authors: Brenner H R , Martin A R
Published: December 2014

1. Isolated cell clusters from ciliary ganglia of 3‐ to 4‐day‐old chickens were used to examine the electrical characteristics and sensitivity to iontophoretically applied acetylcholine (ACh) of normal cells and cells that had been axotomized on the day of hatching. 2. Resting potentials, input resistances and capacitances were the same in axotomized cells as in normal cells. These averaged about 70 mV, 165 Momega and 35 pF respectively. 3. Sensitivity to iontophoretically applied ACh was lower in axotomized cells than in normal cells by a factor of about 8. The rise times of the ACh potentials were the same in the two groups; indicating that the reduced sensitivity was not due to a diffusion barrier. 4. The slopes of the dose‐reponse curves, plotted on a double‐logarithmic scale, suggested that the co‐operative action of two ACh molecules was involved in activating a post‐synaptic conductance channel. This relation was unaltered by axotomy. 5. The estimated reversal potential for the action of ACh was unchanged after axotomy. 6. Cells in isolated clusters were similar to those in intact ganlia with respect to threshold depolarization, amplitude and time course of action potentials and ability to generate repetitive action potentials. There were no differences in these characteristics between normal and axotomized cells. 7. Cells in the isolated clusters had input resistances which were larger by a factor of 2‐3 and capacitances that were smaller by a factor of about 2 than those of cells in intact ganglia. It is suggested that these differences were due to loss of initial segments of axons from the isolated cells. 8. Normal cells in the isolated clusters displayed spontaneous miniature synaptic potentials, indicating that synaptic integrity was maintained during the isolation procedure. As in intact ganglia, no spontaneous activity was observed in axotomized cells.
Inhibition and facilitation of antidromically identified tubero‐infundibular neurones following stimulation of the median eminence in the rat.
Authors: Sawaki Y , Yagi K
Published: December 2014

1. Stimulation of the median eminence of female rats inhibited the spontaneous firing of antidromically identified tubero‐infundibular units. Some units could be inhibited by stimuli subthreshold for the antidromic spike. A conditioning stimulus of subthreshold intensity for the antidromic spike also delayed or abolished the invasion of the soma and dendrites of the same unit by antidromic action potentials evoked by a suprathreshold stimulus given 2‐10 msec later. 2. Although strychnine (0‐2 mg/kg, i.v.) did not significantly alter the inhibition evoked by stimulation of the median eminence, it was abolished by picrotoxin (2‐6 mg/kg, iv.). 3. In seven of the fifty‐seven identified units examined stimulation of the median eminence facilitated the spontaneous firing. However, after an i.v. injection of picrotoxin the facilitory response was observed in thirty‐seven of the forty‐six units tested. Post‐stimulus time histograms obtained from the same unit before and after an injection of picrotoxin demonstrated that the latency and duration of the facilitation did not always coincide with that of the inhibition. 4. After an injection of picrotoxin the field potential evoked by antidromic stimulation of the median eminence consisted of a small positive wave followed by a negative wave. Frequently the negative wave of the field potential was accompanied by a convulsive discharge. The latency of the negative wave appears to be identical to that of the facilitation seen in nearby single units. 5. The facilitation evoked by antidromic stimulation in the presence of picrotoxin was blocked by an i.v. injection of alpha‐methyl‐p‐tyrosine (250 or 375 mg/kg). None of the nine units sampled from rats pre‐treated with alpha‐methyl‐p‐tyrosine injected twice I.P. (250 mg/kg for each) were facilitated by stimulation of the median eminence following I.V. picrotoxin, while eight of the eleven units sampled from control rats pre‐treated with L‐tyrosine could be facilitated by antidromic stimulation. 6. These results suggest that tuber‐infundibular neurosecretory neurones are inhibited and facilitated by neural pathways which could involve the axon collaterals of the neruosecretory neurones which project to the external layer of the median eminence. It is also suggested that GABA‐releasing neurones mediate the inhibition and catecholaminergic neurones are involved in the facilitory pathways. Presumably the facilitation is normally masked by the activity of the GABA‐releasing neurones.
Reversal of the morphological effects of monocular deprivation in the kittens's lateral geniculate nucleus.
Authors: Dürsteler M R , Garey L J , Movshon J A
Published: December 2014

1. Eleven kittens were deprived of vision in one eye until the age of between 5 and 14 weeks. Their eyes were then reverse‐sutured, they were allowed to survive for a further 3‐63 days, and their brains were then examined histologically. 2. Measurement of the cross‐sectional area of cells in the lateral geniculate nucleus (LGN) showed that when the reversal of lid suture was performed at the age of 8 or 14 weeks, the mean cell size was smaller in laminae connected to the initially closed right eye than it was in other laminae. 3. When the reversal of lid suture took place at 5 or 6 weeks of age there was a reversal of interlaminar size differences: the initially deprived eye was then connected to laminae containing larger cells. Even within 3 days after the reversal of lid suture, most of the morphological effects of the initial suture had been abolished, and they were fully reversed within 12 days. 4. These results are compared with physiological changes in the visual cortex of these and similarly reared animals.
The conditions required for the maintenance of binocularity in the kitten's visual cortex.
Authors: Blakemore C
Published: December 2014

1. In young kittens, cortical neurones, which are usually binocularly driven, have their binocularity reduced if one eye is covered, or if the eyes are made strabismic or alternately occluded. Some of the factors causing these changes were analysed. 2. If the contrast of one retinal image is abolished with no difference in mean illumination, the input from that eye is virtually lost. 3. If one eye merely has its mean retinal illumination attenuated, that eye does not specifically lose its influence in the cortex, although there is a reduction in the proportion of binocular units. This change might partly be due to a difference in the timing of signals from the two eyes but is more likely to be caused by a difference in the strength of the discharges. 4. There is little change in binocularity if one image is dimmed but contrast is absent from both. 5. If contours of very different orientation fall simultaneously on corresponding retinal regions, binocularity breaks down, as in the case of strabismus or when different patterns are presented to the two eyes. But as long as the patterns on corresponding retinal points have similar orientation, even if the visual axes are misaligned, binocularity can be maintained. 6. If the eyes are not stimulated simultaneously, binocularity is reduced, even if the contours falling on the two retinae (at different times) are identical. 7. Roughly simultaneous stimulation, with roughly congruent patterns on the two receptive fields, are needed for the upkeep of binocular connexions on to cortical cells.
Asymmetric tonic labyrinth reflexes and their interaction with neck reflexes in the decerebrate cat.
Authors: Lindsay K W , Roberts T D , Rosenberg J R
Published: December 2014

1. Tonic labyrinth and neck reflexes were studied separately and in combination in the decerebrate cat with C1 and C2 spinal roots cut. Reflex effects were observed as changes in length of the isotonically loaded medial head of triceps. 2. The tonic labyrinth reflexes acted asymmetrically on the medial head of triceps. Side‐down rotation of the head produced shortening in medial triceps, whereas side‐up rotations of the head resulted in a lengthening. 3. The tonic neck reflexes acted asymmetrically on the medial head of triceps. Side‐down rotations of the neck produced a lengthening of medial triceps, whereas side‐up rotations of the neck resulted in shortening. 4. Labyrinth and neck reflexes produce opposite effects on the same limb extensor muscle so that, if the neck innervation is intact, head tilting produces no change in muscle length. 5. It is suggested that the interaction between the labyrinth and neck reflexes contributes to the stability of the trunk, allowing the head to move freely on the body without affecting this stability. Labyrinth and neck reflexes need therefore to be considered together as a single system.
Effect of regional alpha‐ and beta‐adrenergic blockade on blood flow in the resting forearm during contralateral isometric handgrip.
Authors: Eklund B , Kaijser L
Published: December 2014

In a previous study we have shown that an isometric handgrip is accompanied by a rapid decrease in vascular resistance in the resting (contralateral) forearm, lasting for about 1 min, which in all probability is neurogenic. 2. In the present study the distribution of the vasodilatation was investigated by analysing O2 saturation in a deep vein, draining mainly muscle tissue. Some possible neurogenic mechanisms for the vasodilatation were tested by repeating the handgrip after local beta‐ and alpha‐adrenergic blockade of the resting forearm with propranolol and phentolamine, respectively. 3. Without blockades the forearm vascular resistance decreased and the deep vein O2 saturation increase to similar degrees on contralateral handgrip. Propranolol markedly reduced both the decrease in resistance and the increase in deep vein O2 saturation. Phentolamine did not alter the initial decrease in resistance, but with phentolamine resistance continued to decrease after 1 min. 4. It is concluded that the rapid decrease in vascular resistance in the resting forearm on contralateral handgrip takes place, to a great extent, in muscle. It is mediated by neurogenic beta‐adrenergic mechanisms and if the contraction is prolonged it gradually changes to a vasoconstriction mediated by alpha‐adrenergic mechanisms.
Early and late hind‐limb vascular responses to stimulation of receptors in the nose of the rabbit.
Authors: Allison D J , Powis D A
Published: December 2014

1. In rabbits under pentobarbitone anaesthesia stimulation of the nasal mucous membrane with ether vapour causes apnoea, bradycardia and a rise in arterial blood pressure. 2. Simultaneous measurements of femoral arterial blood pressure and of femoral arterial or venous blood flow show that vascular resistance increases in both the intact and skinned hind limb in response to nasal stimulation. Evidence is presented to show that the increase in hind‐limb vascular resistance is due to vasoconstriction which is relfex in nature. 3. The change in vascular resistance in the hind limb following nasal stimulation may be divided into two distinct phases. The primary (early) phase is mediated by the efferent sympathetic nerves to the limb whereas the secondary (late) phase is mediated by adrenal gland hormones. 4. The secondary phase of the hind‐limb vascular response is invariably less pronounced than the primary phase, and with regard to the time course of the appearance of the two phases of the response it appears that following stimulation of the nose there is no mutual reinforcement of sympathetic neural and humoral influences on the hind‐limb blood vessels. 5. The cardiovascular response occur in the absence of changes in pulmonary ventilation.
Control of the delayed outward potassium currents in bursting pace‐maker neurones of the snail, Helix pomatia.
Authors: Heyer C B , Lux H D
Published: December 2014

The net outward current in bursting pace‐maker neurones of the snail (Helix pomatia) during sustained and repeated voltage clamp pulses was studied. The properties of currents remaining in cobalt‐Ringer or after TEA injection were compared with those in untreated cells. 2. With sustained voltage clamp depolarizations the net outward current first increases to a maximum at 150 msec and then declines to 60% or less of its peak intensity. This depression, which is greater during repetition of short pulses (e.g. 100 msec pulses at 0‐5 sec intervals), represents a true decrease in the outward flow of K (designated IK) and is not due to a decreased driving force resulting from extracellular K accumulation. The steady‐state current‐voltage (I‐V) relationship for IK is N‐shaped (Heyer & Lux, 1976). 3. A component of IK persists when Ca and Mg in the medium are replaced by Co (ICo‐res). With voltage clamp depolarizations ICo‐res increases rapidly to a maximum and then partially inactivates with voltage dependent time constants of hundredths or tenths of seconds. Repolarization removes the inactivation. Thus, repeated stimulation with short pulses does not increase the depression of ICo‐res‐ICo‐res (e.g. measured during voltage steps from holding potentials of ‐50 to near 0 mV) is smaller in test pulses preceded by depolarization and larger in pulses preceded by hyperpolarization. The steady state I‐V relationship is not N‐shaped. ICo‐res is blocked by intracellular injection of tetraethylammonium (TEA). 4. Repeated voltage clamp depolarization to near 0 mV with 100 msec pulses for neurones with large Ca currents in normal Ringer produces a long‐term depression which is maximal with 300‐400 msec repolarizations (to ‐50 mV) between pulses. This corresponds with stimulus parameters for the maximum Ca current (Heyer & Lux, 1976). Intracellular injection of Ca2+ (also Ba2+ and Co2+) likewise reduces the total net outward current and especially the delayed outward current under voltage clamp. 5. The component of IK which is removed by Co is identified as Ca dependent and designated IK(Ca). With single voltage clamp pulses IK(Ca) follows the approximate time course and voltage dependence of the slow inward Ca current (Iin slow; Heyer & Lux, 1976). Several lines of evidence suggest that Ca ions moving through the membrane activate IK(Ca). 6. Part of IK cannot be blocked by intracellular TEA injection. In different neurones the magnitude of the IK component resistant to TEA (ITEA‐res) is approximately proportional to the relative magnitudes of Iin slow.ITEA‐res does not inactivate with sustained depolarization and shows pronounced long‐term depression with repetitive stimulation at intermediate intervals and an increased outward current at the onset of the second and subsequent pulses following short repolarizations. The steady‐state I‐V relationship is N‐shaped. ITEA‐res is abolished by extracellular Co. 7. A net inward current with low depolarizations can be measured after TEA injection...
The effect of local changes in potassium and bicarbonate concentration on hypothalamic blood flow in the rabbit.
Authors: Cameron I R , Caronna J
Published: December 2014

Blood flow has been measured locally in the hypothalamus of anaesthetized rabbits by measuring the clearance of small volumes (5‐20 mul.) of a mock cerebrospinal fluid solution containing 133Xe. The effect of varying the [K+] or [HCO‐3] of the 133Xe‐containing solution on local hypothalamic blood flow has been investigated. 2. There was an increase in local hypothalamic blood flow if the 133Xe‐containing solution was HCO3‐‐free; raising the [HCO‐‐3,] of the solution to 40 mM caused a fall in local blood flow. 3. There was an increase in local hypothalamic blood flow when 133Xe was injectedin a mock cerebrospinal fluid containing 10 or 20 mM‐[K+]. There was no significant change in blood flow if a K+‐free or a 40 mM [K+] solution was used. 4. The decrease in hypothalamic blood flow caused by injecting a 40 mM‐[HCO3] solution could be reversed by the addition of 20 mM [K+] to the solution. There was no further increase in blood flow if 20 mM‐[K+] was added to a HCO3‐‐free solution. 5. It is concluded that local blood flow in the hypothalamus changes as a result of variation in local [K+] as well as local [HCO‐3]. The changes in blood flow in the brain which accompany neuronal activity could be mediated by variation in local [K+].
Electrical excitability of cultured adrenal chromaffin cells.
Authors: Biales B , Dichter M , Tischler A
Published: December 2014

1. Adult human and gerbil adrenal medullary cells were maintained in dissociated cell culture and studied by micro‐electrode penetration. 2. In the best recordings, chromaffin cell transmembrane potentials exceeded ‐50mV. 3. Chromaffin cells were capable of generating all‐or‐nothing over‐shooting action potentials, similar to those generated by sympathetic neurones. 4. The action potentials were blocked by tetrodotoxin (TTX, 10(‐6)g/ml.) but were not blocked by removal of Ca or by CoCl2 (10 mM). We conclude that the action potentials are probably generated by a Na mechanism. 5. Chromaffin cells are depolarized by the iontophoretic application of acetylcholine (ACh). This depolarization was accompanied by an increased membrane conductance and could trigger action potentials. 6. Action potentials were also found in cells in fresh slices of gerbil adrenal medullae.
Physiological properties and receptive fields of mechanosensory neurones in the head ganglion of the leech: comparison with homologous cells in segmental ganglia.
Authors: Yau K W
Published: December 2014

A study of the head ganglion of the leech was made to compare the properties of specific sensory cells in this ganglion with those of homologous neurones in the segmental ganglia. 1. In the head ganglion, cells were identified that had electrical properties, sensory modalities and adaptation properties similar to those of touch (T), pressure (P) and nociceptive (N) cells in the segmental ganglia. The cell bodies of these neurones were situated in characteristics positions that could be correlated with those in the segmental ganglia. Several lines of evidence suggested that they were primary sensory neurones. Fewer T, P and N neurones were identified in the head ganglion than would be expected from its six constituent segmental ganglia. 2. The receptive fields of identified T, P and N cells were situated on the external surface of the head and the interior of the mouth with considerable overlap. They were generally smaller in size than those situated on the main part of the body. The receptive fields were also displaced anteriorly so that some of them were situated in segments anterior to those of the innervating cells. 3. The morphology of the sensory cells in the head ganglion was studied by intracellular injection of horseradish perioxidase. The general branching characteristics of the cells and the structural appearance of their processes resembled those of homologous cells in the segmental ganglia. However, the routes taken to the periphery by some of the cells were not constant from head ganglion to head ganglion. This variability was confirmed by electrophysiological evidence, and differed from the constancy seen in segmental sensory cells.
The bicarbonate ion pump in the endothelium which regulates the hydration of rabbit cornea.
Authors: Hodson S , Miller F
Published: December 2014

1. Studies were made on the short‐circuit current (s.c.c.) and fluid transport across rabbit corneal endothelium. 2. Normal s.c.c. of 27 muA.cm‐2 is reduced to 19 muA.cm‐2 in CO2‐free Ringer, to 9 muA. cm‐2 in HCO‐3 ‐free Ringer and to zero in CO2 and HCO‐3 ‐free Ringer. 3. Carbonic anhydrase inhibitors reduce s.c.c. from 27 to 19 muA.cm‐2. Removal of exogenous CO2 causes no further reduction in s.c.c. 4. In CO2‐free Ringer, net exogenous bicarbonate translocation is equal to s.c.c. 5. In all cases studied, net fluid transport across the endothelium in open circuit is directly proportional to s.c.c. 6. It is concluded that the endothelial 'pump' which regulates corneal hydration operates by 'pumping' bicarbonate ions into the aqueous humour. 7. Under physiological conditions, two thirds of the substrate is supplied by exogenous bicarbonate ions and one third is supplied by conversion of exogenous CO2 by intracellular carbonic anhydrase. 8. Metabolic CO2 does not participate significantly in the process, probably because it is at too low a concentration to compete effectively with exogenous CO2. 9. Electron histochemical studies suggest that carbonic anhydrase is located immediately underneath the posterior membrane of the endothelium, across which the active bicarbonate ion flux passes.
The formation and regression of synapses during the re‐innervation of axolotl striated muscles.
Authors: Bennett M R , Raftos J
Published: December 2014

1. A study has been made of the formation and regression of synapses formed by spinal nerves 16 and 17 in axolotl hind‐limb flexor muscles following the severing of nerve 16, using histological, ultrastructural and electrophysiological techniques. 2. Axolotl hind‐limb flexor myofibres possessed 'en plaque' end‐plates from either spinal nerve 16 or 17 or both at intervals of about 1000 micronm along their length; the myofibre's length constant was about 700 micronm allowing electrophysiological observations of at least two of these synapses during a single impalement; transmitter release at these synapses could be described by binomial statistics and in a given set of ionic conditions the binomial statistic parameter n was directly proportional to the size of the nerve terminals whilst the binomial statistic parameter p was invariant to changes in nerve terminal size. 3. The distribution of synapses formed by spinal nerves 16 and 17 in different sectors of the axolotl hind‐limb flexor muscles was determined from a study of evoked end‐plate potentials; the middle and proximal sectors of the flexor muscles contained myofibres which received an innervation from nerve 16 only, whereas the sectors surrounding these contained myofibres innervated either by nerve 16 or nerve 17 or by both nerves. 4. Six days following the severing of spinal nerve 16, evoked transmitter release from the synapses formed by this nerve had failed; transmission was subsequently recorded at a few synapses formed by nerve 17 in the middle and proximal sectors of the flexor muscles which are not normally innervated by this nerve and these synapses had a low n; during the succeeding four weeks the value of n at the synapses increased to a size about 70% that of the terminals normally formed by nerve 16 at these sites. 5. Four weeks after severing nerve 16, myofibres which possessed synapses formed by nerve 17 also possessed synapses from re‐innervating nerve 16 and these were sometimes formed at the same synaptic sites as those occupied by nerve 17. 6. In the subsequent sixteen weeks, the n value of synapses formed by nerve 17 declined whilst the n values of synapses formed by re‐innervating nerve 16 on the same myofibres matured to their control size. 7. It is suggested that on severing nerve 16 collateral sprouting of nearby intact nerve 17 occurs and these collateral sprouts innervate the denervated synaptic sites, although the sprouts arenot as well matched to the denervated synaptic sites as are the original nerve terminals; thus if nerve 16 returns it preferentially forms synapses at its original synaptic sites, and the collateral synapses formed by nerve 17 regress.
Cellular and extracellular dehydration, and angiotensin as stimuli to drinking in the common iguana Iguana iguana.
Authors: Fitzsimons J T , Kaufman S
Published: December 2014

1. After water deprivation, the iguana promptly drank slightly more than enough water to restore the body fluids to isotonicity even under conditions of hypervolaemia. 2. In response to systemic injections of hypertonic solutions of NaCl and sucrose, the iguana drank and retained enough water to dilute the injected load to isotonicity irrespective of whether water was offered immediately or after 3 hr, and irrespective of whether the solute was administered I.V. or I.P. 3. Hypertonic solutions to glucose, urea, sorbitol and KCl caused little drinking. 4. The long latencies to drinking after hypertonic loads, which were not dependent on the nature of the solute, the route of administration or the dosage, were shown not to be a result of slow distribution of the solute throughout the body fluids. 5. Clearance of injected solutes via renal and extra‐renal (nasal salt gland) routes was negligible during the 6 hr experimental period. 6. Measurements of plasma [Na], haematocrit, osmotic pressure and inulin space showed that the iguana drank, in response to cellular dehydration, enough water to restore the intracellular fluid volume to normal. 7. We conclude that, in response to substances which dehydrate cells, the iguana regulates its body osmolality precisely and efficiently provided it is able to do so by drinking. In this respect the responses of the iguana are similar to those of the nephrectomized rat since, in the short term, both rely exclusively on drinking to restore cellular water to normal. 8. The iguana also drinks in response to extracellular dehydration produced by hyperoncotic peritoneal dialysis, and in response to I.P. angiotensin II.
The sensory mechanism of servo action in human muscle.
Authors: Marsden C D , Merton P A , Morton H B
Published: December 2014

1. Anaesthesia of the thumb suppresses servo action in the long flexor of the thumb during movements of the terminal phalanx. 2. It needs a greater subjective effort to flex an anaesthetized thumb than a normal one. 3. Anaesthesia of other digits is without effect on the thumb flexor. 4. In an anaesthetic thumb without servo responses the changes in force exerted when a mechanical perturbation is applied which are due purely to the passive mechanical properties of the muscle can be measured. Subtraction of these gives the active components of servo action in the normal thumb and thus an estimate of the mechanical gain of the servo. 5. Giving the subject a visual tracking task can partially restore servo action when the thumb is anaesthetic. 6. After some years subjects become resistant to the effect of peripheral anaesthesia. 7. Peripheral anaesthesia has no detectable effect on servo responses in the long flexor of the great toe, in infraspinatus or in pectoralis major. Servo action in these muscles is presumably based predominantly on muscle receptors. 8. Tendon jerks are not apparently influenced by peripheral anaesthesia. 9. The Discussion considers the possibility that, for the thumb, muscle afferents co‐operate with a somatic and a visual input in a servo loop via the cerebral cortex.
Cutaneous facilitation of transmission in reflex pathways from Ib afferents to motoneurones.
Authors: Lundberg A , Malmgren K , Schomburg E D
Published: December 2014

1. The effect of volleys in low threshold cutaneous afferents upon transmission of synaptic action from Ib afferents to motoneurones has been investigated with intracellular recording from alpha motoneurones to hind limb muscles. 2. There was facilitation from cutaneous afferents of transmission in excitatory and inhibitory reflex pathways from Ib afferents without any evidence for difference in effect on di‐ and trisynaptic pathways. It is postulated that volleys in cutaneous afferents evoke excitatory action in interneurones of these reflex pathways. 3. The time course of the facilitation suggest that cutaneous afferents have disynaptic excitatory connexions with the interneurones intercalated in the disynaptic Ib inhibitory pathways to motoneurones. 4. Some observations are reported suggesting that interneuronal transmission in Ib inhibitory pathways to motoneurones might be facilitated from Ia afferents. 5. The findings are discussed in relation to the presumed role of Ib reflex action in regulating muscle tension.
The effects of histamine on skeletal muscle vasculature in cats.
Authors: Flynn S B , Owen D A
Published: December 2014

1. Experiments have been made to determine the vascular effects of histamine and the mechanism of histamine‐induced oedema formation in cat skeletal muscle. 2. Histamine caused dose‐dependent dilatation of resistance vessels and increased intravascular volume over the dose range 1 X 10(‐10)‐1 X 10(‐8) mol/kg min. The dilatation of resistance vessels resulted in dose‐dependent increases in capillary hydrostatic pressure. 3. Histamine increased vascular permeability, as measured by accumulation of [131I]human serum albumin in the tissue, during infusions at 1 X 10(‐8) mol/kg min but no albumin accumulation could be detected at lower infusion rates. 4. Oedema formation during histamine infusion of 1 X 10(‐10) and 1 X 10(‐9) mol/kg min seemed to be due to increases in capillary hydrostatic pressure and independent of increased vascular permeability. During infusions of histamine 1 X 10(‐8) mol/kg min oedema was due predominantly to increased vascular permeability and to a lesser extent, the increase in capillary hydrostatic pressure.
Effects of glucagon on canine intestinal sodium and water fluxes and regional blood flow.
Authors: MacFerran S N , Mailman D
Published: December 2014

1. Glucagon (0‐05 or 0‐5 microng/kg. min) was infused into a mesenteric artery of a canine ileal segment from which transport was measured (direct infusion) or into a mesenteric artery of an adjacent non‐perfused segment (indirect infusion). Unidirectional Na and H2O fluxes and arterial and mesenteric vein pressures and total and absorptive site blood flows were measured. 2. Direct glucagon infusion increased the absorptive and secretory fluxes of Na and H2O and absorptive site blood flow, and decreased absorptive site resistance and arterial and mesenteric vein pressure. Indirect glucagon infusion had the opposite effects. 3. Neither the direct arterial infusion of histamine (0‐1‐53 microng/kg. min) nor the I.V. infusion of glucose (0‐2 g/min) or insulin (0‐1 micron/kg) or glucose plus insulin, mimicked the effects of glucagon. 4. The unidirectional secretory and absorptive fluxes of both Na and H2O were linearly related to the calculated capillary pressure during glucagon infusion. 5. It was concluded that the effects of glucagon on gut transport were due to effects exerted through the cardiovascular system.
Temperature and amplitude dependence of tension transients in glycerinated skeletal and insect fibrillar muscle.
Authors: Abbott R H , Steiger G J
Published: December 2014

1. Quick stretches and releases were applied to small bundles of glycerinated fibres of rabbit psoas and insect fibrillar flight muscle. The resulting tension changes were recorded at various temperatures and amplitudes of length change. The results from the two preparations had many features in common. At temperatures near 0 degrees C the asymmetry of the initial tension recovery after stretch and release originally reported in living frog fibres by Huxley & Simmons (1971 alpha) was very obvious. 2. The complete tension course could be described as an elastic change occurring simultaneously with the length change followed by recovery consisting of the sum of a number of exponential terms. These terms usually corresponded to the phases discernible without curve fitting, but in some cases a monotonic rise or fall of tension was seen to consist of two components only after curve fitting. 3. After either stretch or release there was a phase of rapid tension recovery towards the value before the length change. The rate constant of this phase increased as the amplitude of stretch or release was increased to about 2 nm/half sarcomere. At higher amplitudes it remained nearly constant 4. At temperatures near 0 degrees C there was a second and much slower continuation of the recovery after stretch. The rate constant of this second phase was much more sensitive to temperature than that of the first phase and it became slower with increasing amplitude of stretch. As the temperature was raised the speed of the second phase approached the speed of the first phase so that at room temperatures the initial tension recovery after stretch and release was nearly symmetrical. 5. Under many conditions these processes were followed by a change in the opposite direction, the 'delayed tension' described by earlier workers. This third phase of tension change had about the same temperature sensitivity as the second phase of the recovery seen after stretch. The tension due to stretch activation was not maintained in rabbit muscle, resulting in a fourth possible phase, a recovery of tension towards the value before the length change. This was absent or of low amplitude in insect flight muscle. 6. We interpret these tension changes on the basis of an extension of the non‐linear model described by White & Thorson (1972). The elastic tension change and the initial fast recovery are both supposed to be properties of the attached cross‐bridges, whilst the slower recovery is considered to be due to the detachment of cross‐bridges which happened to be attached at the instant the length change was applied. The delayed tension reflects the approach to equilibrium of the number of attached bridges, changed by an effect of muscle length on the attachment rate. The fact that the delayed tension is not maintained in rabbit psoas muscle may be due to the effect of length on attachment rate being transitory.
Sleep and respiration of rats during hypoxia.
Authors: Pappenheimer J R
Published: December 2014

1. The effects of hypoxia on slow‐wave sleep (SWS) and of SWS on respiratory responses to hypoxia were investigated on rats provided with chronically implanted cortical electrodes. 2. During the daytime (5‐7 hr periods) the proportion of time spent in SWS was 45% (S.E. +/‐ 1.0%) when the rats breathed air. Exposure to 10% O2 (equivalent to 18,000 ft.) reduced this proportion to 27% (S.E. +/‐ 2.5%). During hypoxia the intensity of e.e.g. activity in SWS (mean, rectified slow‐wave voltage) rarely equalled the normal values characteristic of the same rats in fully developed SWS breathing air. The normal pattern of 5‐15 min episodes of SWS was changed by hypoxia to a series of brief (2‐3 min) incompletely developed episodes. 3. Addition of CO2 to inspired gas failed to prevent the reduction of SWS during hypoxia. CO2 in normal O2 did not alter sleep significantly. The effects of hypoxia on sleep therefore depend upon changes in O2 pressure rather than upon changes in CO2. 4. The effect of SWS on respiration of rats breathing air was to decrease frequency and minute volume by 10‐20%. In hypoxia, however, the frequency increased markedly when the animals entered SWS ; minute volume was not significantly changed. It follows that stimulation of breathing by hypoxia is greater during SWS than during wakefulness. 5. The anomalous increase of respiratory frequency when hypoxic rats entered SWS was abolished by addition of CO2 to the hypoxic gas mixture. 6. Steady‐state gaseous metabolism (Vo2 Vco2) was decreased 18 +/‐ 3% during hypoxia and was increased 31 +/‐ 4% during exposure to 5% CO2. The implications of these changes for interpretation of respiratory responses to O2 and CO2 are discussed.
Extracellular potassium and trasmitter release at the giant synapse of squid.
Authors: Erulkar S D , Weight F F
Published: December 2014

1. The effects of changes in extracellular K concentration, [K]0, on synaptic transmission were studied at the squid giant synapse with intracellular recording from the presynaptic terminal and post‐synaptic axon. 2. The amplitudes of both the presynaptic spike and the e.p.s.p. varied inversely with [K]0. On the average, a 10 mV change in spike height was accompanied by a 3‐1 mV change in e.p.s.p. amplitude. 3. The amplitude of the presynaptic spike after‐hyperpolarization (AH) varied inversely with [K]0. On the average, increasing [K]0 resulted in a 20% change in e.p.s.p. amplitude per mV change in presynaptic spike AH. 4. Repetitive antidromic stimulation of the post‐synaptic giant axon resulted in an exponential decline in the post‐synaptic spike AH, a depolarization of the presynaptic membrane potential and a reduction in the AHs of presynaptic spikes. This suggests that the K which accumulates in the extracellular spaces around the post‐synaptic axon also affects the presynaptic terminal. 5. Repetitive antidromic stimulation of the post‐synaptic axon resulted in a reduction in the amplitude of e.p.s.p.s. elicted by stimulation of the presynaptic axon. The reduction in e.p.s.p. amplitude relative to the change in presynaptic spike AH was quantitatively close to the change produced by increasing [K]0, suggesting that the reduction in e.p.s.p. amplitude is due to the accumulation of extracellular K at the presynaptic terminal. 6. Repetitive stimulation of the presynaptic axon reduced the amplitudes of the e.p.s.p. and the presynaptic spike AH. On the average, a 1 mV change in presynaptic spike AH was accompanied by a 204% change in e.p.s.p. amplitude, suggesting that K accumulation may only contribute to a small extent, under these conditions, to the depression of transmitter release.
Body fluid changes which influence drinking in the water deprived rat.
Authors: Ramsay D J , Rolls B J , Wood R J
Published: December 2014

1. After overnight deprivation of water both the cellular and extracellular fluid volumes are significantly reduced in the rat. 2. In the rat with functional kidneys oral, intragastric or intravenous preloads of 10 ml. water reduce the total water intake after 1 hr by 64‐69%. These preloads restore plasma osmolality to pre‐deprivation levels but have little effect on plasma volume. 3. In the same rats if the plasma volume is restored with an oral, intragastric or intravenous preload of 10 ml. of an isotonic balanced salt solution which has little effect on osmolality, drinking is significantly reduced by 20‐26%. The reduction of drinking correlated with the volume of the preload of balanced salt. 4. Plasma analysis shown that 1 hr after an oral preload of 10 ml. isotonic balanced salt solution, the extracellular fluid volume of the deprived rats is restored to pre‐deprivation levels but osmolality is unchanged. Three hr after the balanced salt preload, extracellular fluid volume is still at pre‐deprivation levels and there has been a slight decrease in osmolality due to excretion of salt. 5. In rats which had been nephrectomized or had the ureters ligated so there could be no renal modification of the preloads, the effects of the preloads of water and balanced salt are the same as in rats with intact kidneys. 6. The results indicate that after water deprivation in the rat, changes in both the cellular and extracellular fluid compartment are stimuli to drinking.
The concentration of ionized magnesium in barnacle muscle fibres.
Authors: Brinley F J , Scarpa A , Tiffert T
Published: December 2014

1. The total Mg in isolated fibres of Balanus aquila was 10‐5 m‐mole/kg wet wt. 2. The intracellular free Mg was measured by a null point method using Eriochrome Blue as an indicator of free Mg, and internal dialysis with solutions of varying ionized Mg concentrations. The results indicated a free Mg of 6 mM or 4‐2 m‐mole/kg wet wt. in the intracellular water immediately surrounding the dialysis capillary. 3. The ATP concentration was estimated to be 4‐9 m‐mole/kg wet wt. 4. A tentative partitioning of Mg among various intracellular constitutents based on present data combined with published work by others is (m‐mole/kg wet wt): free, 4‐2; MgATP, 4‐2; myofibrillar bound, 1; residual (presumably bound to arginine phosphate and phosphate) ca. 1.