bluuebunny/crossref_metadata_2025 huggingface dataset:
Detachment of structurally intact nerve endings from chromatolytic neurones of rat superior cervical ganglion during the depression of synaptic transmission induced by post‐ganglionic axotomy.
Authors: Matthews M R , Nelson V H
Published: December 2014

1. Electrophysiological studies showed that injury of post‐ganglionic nerve fibres leads to severe and prolonged depression of synaptic transmission through the rat superior cervical ganglion, beginning within 24 h. This is in line with the results of previous studies in other species and upon other neurones. 2. electron microscopy after post‐ganglionic axotomy revealed nerve endings of presynaptic type with all the specialized membrane‐related features of a synaptic zone, but which were not apposed to any post‐synaptic nervous element. These umusual profiles were interpreted as detached presynaptic nerve endings. In normal and control ganglia, such profiles formed at most 0–5% of all vesicle‐containing profiles of presynaptic type; in ganglia with all major post‐ganglionic branches cut the proportion rose to approximately 7%, between 3 and 7 d post‐operatively. Over this period, the mean incidence of chromatolytic neurones was 74–6%. 3. Concomitantly, the incidence of synapses within the ganglion fell by about 75%, reaching its lowest levels between 3 and 7 d post‐operatively. There was strikingly little evidence of persistence of post‐synaptic membrane specializations (‘membrane thickenings’) following detachment of synapses. 4. At longer survival intervals the incidence of synapses gradually increased, and that of detached nerve endings gradually decreased; recovery was well advanced by 42 d. 5. The fall in the incidence of synapses was closely paralleled by a fall in the incidence of desmosome‐like attachments in the ganglion; the incidence of such attachments was found to be correlated to a significant degree with that of synapses. 6. It is concluded that most or all of the synapses upon sympathetic neurones become physically dissociated during the chromatolytic reaction of these neurones to axotomy. The failure to persist of ultrastructurally specialized post‐synaptic sites, and the loss of desmosomes (particularly marked for those involving purely post‐ganglionic nervous elements) suggest that the post‐ganglionic neurone is losing all its specializations for attachment. 7. Some evidence suggests that the satellite cells may effect the final separation between pre‐ and post‐synaptic structures.
Organization of climbing fibre projections to the cerebellar cortex from trigeminal cutaneous afferents and from the SI face area of the cerebral cortex in the cat.
Authors: Miles T S , Wiesendanger M
Published: December 2014

1. In cats anaesthetized with pentobarbitone, the projection of climbing fibres (CFs) to the cerebellar cortex from trigeminal cutaneous branches and from the face area of the sensorimotor (SI) cortex was mapped, using the technique of laminar field potential analysis. 2. The CF projections from both the trigeminal nerve and the SI face area were found to be localized to the same cerebellar folia, viz. chiefly the ipsilateral lobule HVI, with a small overlap on to the adjacent folia of lobule V and crus Ia of HVIIA. Frequently a projection from the superficial radial nerve to part or all of this area, was also found. 3. A correspondence in the distribution and amplitudes of CF potentials evoked at most points by stimulation of the trigeminal nerve and the SI cortex was found. This implies a convergence of afferents from these two sources at or before the inferior olive. 4. In more than half of the cats, a small area of the cerebellar hemisphere was found, in which contralateral as well as ipsilateral trigeminal stimulation would evoke CF potentials. Usually inputs from the superficial radial nerve and the SI cortex also converged upon this area. 5. The organization of CF projections from trigeminal and superficial radial nerve afferents to the cerebellar hemisphere was found to occur in the same ‘patchy’ pattern of somatotopy that has been described for spinal nerve inputs to the anterior lobe. 6. One constant factor was found in the pattern of organization of CF projections to this area from cutaneous afferent nerves. That is, only the afferents from overlapping areas of skin projected to a given recording point: no instance of CF projections from trigeminal branches innervating discontinuous skin areas was observed.
Voltage‐current relationship of a carbachol‐induced potassium‐ion pathway in Aplysia neurones.
Authors: Ginsborg B L , Kado R T
Published: December 2014

1. The electrical characteristics of a potassium ion selective pathway produced by the action of carbachol on Aplysia neurones (Kehoe, 1972b) has been studied. 2. The relationship between current and voltage has been found to be non‐linear, the conductance increasing with depolarization and decreasing with hyperpolarization. The degree of rectification was reduced when the external potassium was raised to 50 mM from its normal value of 10 mM. 3. The direction of the rectification and the effect of increased potassium are as predicted by the ‘constant field’ theory, but the degree of rectification is somewhat larger.
Cones excite rods in the retina of the turtle.
Authors: Schwartz E A
Published: December 2014

The intracellular responses of rods in the retina of the turtle, Chelydra serpentina, were studied with brief flashes of monochromatic light. 1. Flashes of red or green light applied over an area 25 mum in diameter produce responses with the same shape. With such restricted stimuli, the spectral sensitivity of a rod agrees well with the absorption spectrum of the porphyropsin pigment contained in its outer segment. 2. With stimulating spots more than 500 mum in diameter, dim flashes of red or green light produce responses having different shapes. When the spectral sensitivity of a rod is tested using dim lights of large diameter, the sensitivity to red light is much greater than predicted by the absorption spectrum of porphyropsin. 3. The shape of the response produced by large diameter spots of dim, red light resembles that of cones. 4. Increasing the diameter of a dim, red spot beyond 500 mum markedly alters the amplitude and shape of responses from horizontal cells but does not significantly affect the response of rods. It is concluded that rods receive an excitation from neighbouring cones. This interaction is unlikely to be mediated by type I luminosity horizontal cells but may be mediated by either direct connexions between cones and rods or by an interneurone with a small receptive field.
The sensitivity of paramedian reticular neurones to acetylcholine.
Authors: Duggan A W , Game C J
Published: December 2014

1. Of paramedian reticular neurones a significantly higher proportion of those antidromically activated from the cerebellum than of those orthodromically activated from this source were excited by acetylcholine. 2. Receptors for acetylcholine were of the muscarinic type. 3. No differences were found in the proportions of cholinoceptive and non‐cholinoceptive cells responding to stimulation of cranial and limb nerves or to changes in blood pressure either spontaneous or induced. 4. Either a cholinergic pathway to paramedian reticular cells projecting to the cerebellum was not activated in these experiments or the receptors for acetylcholine are not located at synapses. An association between muscarinic receptors and acetylcholinesterase may be present with cells of this area.
Plasma catecholamines in foetal and adult sheep.
Authors: Jones C T , Robinson R O
Published: December 2014

1. Foetal and maternal plasma catecholamine concentrations were measured during and after hypoxia (mean maternal Pa,02 44mmHg) in chronically catheterized sheep, 118–141 days pregnant. 2. In most foetuses the initial plasma catecholamines were smaller than 0.07 ng/ml. During hypoxia plasma adrenaline and noradrenaline always rose; there was a rise in arterial pressure and a fall in heart rate. 3. The initial catecholamine concentration in the ewes was smaller than 0.05–2.3 ng/ml. During hypoxia there was no consistent change; the maternal plasma concentrations were less than the foetal. 4. Infusion of adrenaline at 0.3 mug kg(−1) min(−1) to the ewe resulted in plasma catecholamine concentrations higher than those observed during hypoxia. There was a rise in heart rate but no consistent change in arterial pressure. 5. Infusion of adrenaline 0.4 mug kg(−1) min(−1) into the foetal jugular vein caused a rise in plasma concentration similar to that seen during hypoxia. There was a rise in heart rate but no significant change in arterial pressure. 6. The half‐life of adrenaline and of noradrenaline in the maternal and foetal circulation was 0.25‐1 min. There was no evidence of transfer of labelled catecholamine across the placenta.
Physiological identification of a morphological class of cat retinal ganglion cells.
Authors: Cleland B G , Levick W R , Wässle H
Published: December 2014

1. Small selected patches of retina (approximately 1 mm2) were exhaustively searched electrophysiologically to identify every brisk‐transient unit present. The patches were then marked by electrolytic lesions. 2. Whole‐mount preparations were made from which the distribution of alpha cells within and around the marked areas could be obtained. 3. A one‐to‐one correspondence could be demonstrated between brisk‐transient units and alpha cells. 4. The correspondence was maintained within a patch of retina including the central area. 5. The correspondences were subject to about 10% of uncertainty attributed to technical limitations of the method.
Properties of centre‐hyperpolarizing, red‐sensitive bipolar cells in the turtle retina.
Authors: Richter A , Simon E J
Published: December 2014

1. Responses of centre‐hyperpolarizing, red‐sensitive bipolar cells were studied by intracellular recording in the retina of the turtle, Pseudemys scripta elegans. The identity of these cells was confirmed by Procion Yellow marking. 2. Circles of light produced hyperpolarizing waves that were graded with intensity and could exceed −30mV in amplitude. The operating intensity range was similar to that of turtle cones. 3. Flashes in the form of an annulus evoked graded depolarizations which could be greater than 10 mV in the dark‐adapted state or about 30mV when applied over central backgrounds. 4. Responses proportional to intensity were produced by dim circular stimuli. For radii less than about 200 mum these responses reached peak in approximately 120 msec and were invariant with respect to wave‐length or area of illumination. Absolute flash sensitivity varied greatly from cell to cell but in the most sensitive cell encountered was about 460 muV photon(−1) um2. 5. Sensitivity of both bipolar cells and red‐sensitive cones was enhanced progressively for enlargements of a circular flash up to 150–200 mum in radius. 6. Increasing the radius of a circle from 200 to 1250 mum caused a decrease of about 75% in bipolar cell sensitivity. This decrease was associated with a marked shortening of the response for all colours. The same enlargement decreased sensitivity of red‐sensitive cones by approximately 20% and did not appreciably alter the time course of their response. These effects are attributed to impingement from type I red‐sensitive horizontal cells because they have the requisite spatial and spectral properties. 7. Responses of a few bipolar cells were already shortened for 200 mum flashes; this property suggests impingement from type II horizontal cells. 8. For small circles the spectral sensitivity of the bipolar cells considered resembled closely that of red‐sensitive cones or horizontal cells. Red backgrounds enhanced the relative sensitivity to green flashes suggesting that these bipolar cells receive input from red‐sensitive members of double cones as well as single red‐sensitive cones. 9. Steady depolarizing currents injected into bipolar cells decreased the response to either central or annular illumination; hyperpolarizing currents decreased the response to a central flash and increased the response to an annulus.
Effects of ionic concentration on sodium permeability properties of myelinated nerve fibres of Xenopus laevis.
Authors: Brismar T , Frankenhaeuser B
Published: December 2014

1. The nodal currents of single myelinated nerve fibres were recorded under potential clamp conditions, and the effect of [Ca], [Na] and [K] in the external solution on some of the Na permeability properties were analysed. 2. [Ca], [Na] and [K] all affected the position of the steady‐state Na inactivation (h) curve on the potential axis. The curve was displaced in positive direction by high ionic concentration. 3. The shift associated to different [Ca] was largest in low [Na] and [K]. Similarly the shift associated to different [Na] and [K] was largest in low [Ca]. 4. The maximum peak sodium permeability (max. peak — PNa) was affected by the [Ca], [Na] and [K]. It was greater in (i) low [Ca], (ii) high ([Na] + [K]) and (iii) high [Na]:[K] ratio. 5. The effect of [Ca] on peak — Na was mainly a consequence of a change in PNa (which is the value of PNa if activation were complete, m = 1, and inactivation fully removed, h = 1).
Projections of pyramidal tract cells to alpha‐motoneurones innervating hind‐limb muscles in the monkey.
Authors: Jankowska E , Padel Y , Tanaka R
Published: December 2014

1. We have investigated the spatial organization of monosynaptic corticospinal projections to hind‐limb motoneurones, using near threshold stimulation of the surface of the precentral gyrus to activate pyramidal tract (PT) cells and intracellular recording from motoneurones to detect the resulting e.p.s.p.s. 2. Monosynaptic e.p.s.p.s. of cortical origin were seen in all motoneurone species investigated, those of distal as well as of proximal hind‐limb muscles. The proportion of motoneurones in which the e.s.p.s. were evoked and the amplitudes of the latter indicated a more extensive cortical projection to motor nuclei for distal than for proximal muscles, as previously found for forelimb motoneurones. 3. Cortical areas from which monosynaptic e.p.s.p.s. were evoked in individual motoneurones were remarkably large, most often between 3 and 7 mm2. Several motoneurones appeared to have two or three separate areas within the hind‐limb division of the motor cortex. 4. Areas of location of pyramidal tract cells projecting to various motoneurones innervating one muscle were usually not identical. They overlapped often only partially or did not overlap at all. 5. Areas of location of pyramidal tract cells projecting to motor nuclei for different muscles often showed an extensive overlap. When it occurred, various motoneurones of a given motor nucleus had common cortical projection areas with motoneurones of other motor nuclei, either to synergistic or to antagonistic muscles. Our results give further evidence for overlapping of areas of cortical projections to motoneurones and speak against a mosaic‐like organization of pyramidal tract cells projecting to different motor nuclei. 6. The rise times of cortically evoked e.p.s.p.s. indicate that the corticospinal tract fibres terminate on motoneurones at approximately similar distances from the soma as group Ia afferents. The small amplitudes of the majority of e.p.s.p.s. evoked by near threshold cortical stimulation therefore suggest that unitary e.p.s.p.s of cortical origin are small and that the density of pyramidal tract cells projecting to individual motoneurones is usually low, even in the centrum of projection areas. 7. Effects of intracortical stimulation depended on the stimulus strength. With currents of 2‐3 muA, e.p.s.p.s were usually evoked in one motoneurone species or in close synergists. With currents of 5‐10 muA, largest e.p.s.p.s a number of other motoneurones. Latencies of descending volleys in the lumbar corticospinal tract indicated that intracortical stimuli activated pyramidal tract cells indirectly; the effects of these stimuli could thus not be used to indicate the location of pyramidal tract cells responsible for them.
Aerobic and anaerobic metabolism in smooth muscle cells of taenia coli in relation to active ion transport.
Authors: Casteels R , Wuytack F
Published: December 2014

1. The O2 consumption and lactic acid production of the guinea‐pig's taenia coli have been studied in relation to the active Na‐K transport, in order to estimate the ratio: active Na extrusion/active K uptake/ATP hydrolysis. 2. By applying different procedures of partial metabolic ingibition, it was found that a reactivation of the active Na‐K transport in K‐depleted tissues could occur in an anaerobic medium, provided glucose was present and in an aerobic medium free of added metabolizable substrate. The active Na‐K transport was rapidly blocked in an anaerobic‐substrate free medium. 3. Readmission of K to K‐depleted tissues under aerobic conditions stimulates both O2 consumption and lactic acid production. While the O2 consumption creeps up slowly and requires 50 min to reach control values, the aerobic lactic acid production increases to a maximum within 10 min and decreases again during the next 50 min to its steady‐state value. 4. A reactivation of the Na‐pump in K‐depleted cells in a N2‐glucose medium causes an immediate increase of the lactic acid production, which decreases to its control value after 60 min. The maximal increase in anaerobic lactic acid production during reactivation of the Na‐K pump is a function of [K]O. The system can be cescribed with first order kinetics having a Vmax = 0–72 mumole.g‐1 f. wt. min‐1 and a Km = 1‐1 mM. 5. By varying the glucose concentration of [K]O during reactivation of the Na‐K pump, different Na‐K pumping rates can be obtained. The ratios net Na extrusion/ATP or net K accumulation/ATP amount to −1–32 +/− 0–19 (36) and 1‐02 +/− 0–11 (36), in the experiments with different glucose concentrations. Taking into account the interference by net passive fluxes, one can estimate a ratio:active Na transport/active K transport/ATP, of 1‐7/0–8/1. This ratio is not very different from the values observed in other tissues.
Amino acid movements across the wall of anuran small intestine perfused through the vascular bed.
Authors: Boyd C A , Cheeseman C I , Parsons D S
Published: December 2014

1. L‐leucine transfer across the wall of the small intestine has been studied in a vascularly perfused preparation from four species of frog. Some properties of the preparation are described. 2. A description is given of the endogenous amino acids appearing in the vascular bed and of the kinetic properties of this washout of endogenous L‐leucine. 3. In the steady state of absorption, the transfer function relating the net flux of exogenous L‐leucine into the vascular bed to the concentration in the lumen exhibits saturation. Under the conditions of the experiments the apparent concentration in the lumen for half‐maximum transfer of L‐leucine is found to be 2‐1 +/− 0–4 (5) mM. 4. When Na ions are removed from the lumen the transfer of L‐leucine into the vascular bed is inhibited. However, the additional removal of Na ions from the fluid in the vascular bed is further inhibitory to the transfer of the amino acid. 5. L‐leucine previously absorbed from the lumen appears in the vascular bed in a biphasic fashion. Estimates are deduced of the size of the pool of L‐leucine within the tissue which drains into the vascular bed. 6. These results are discussed in relation to previous work on amino acid transport undertaken with various sorts of preparation of small intestine.
Some differences in contractile responses of isolated longitudinal and circular muscle from the guinea‐pig stomach.
Authors: Kuriyama H , Mishima K , Suzuki H
Published: December 2014

The mechanical and electrical properties of the longitudinal (fundus and corpus) and circular (antrum) muscle fibres of the guinea‐pig stomach were investigated. 1. In the longitudinal but not in the circular muscle isotonic K Krebs and Na‐free (sucrose) Krebs solutions produced a contracture with a tonic component. The different mechanical responses were not accompanied by different membrane responses. Verapamil abolished both phasic and tonic components of K‐induced contracture. 2. During the tonic response of the K‐induced contracture, repolarization of the membrane by current pulses relaxed the tissue; after cessation of the current pulse, rebound contracture occurred. In the circular muscle, the Q10 value for the rate of relaxation induced by inward current pulse was 3‐1 and for the development of rebound contracture was 2‐4. 3. After the tissue had been immersed in Ca‐free isotonic K Krebs solution, application of Ca produced a large contracture in the longitudinal muscle, but contracture in the circular muscle was small or absent. However, the amplitude of subsequent carbachol‐induced contracture in the above solution was enlarged in proportion to the durations of Ca treatment in both tissues. 4. Direct tetanic electrical stimulation could produce tension in both tissues. With low frequency of stimulation (0‐1 Hz) a positive staircase was observed in the circular but not in the longitudinal muscle. 5. It is concluded from these results that topical differences of the motility in the stomach may be due not only to the activity of nervous elements, but also to differences in the properties of the muscle fibres themselves.
Evidence against a physiological role of prostaglandins in the regulation of noradrenaline release in the cat spleen.
Authors: Dubocovich M L , Langer S Z
Published: December 2014

1. The effects of prostaglandins E2 (PGE2) and indomethacin on responses and on noradrenaline overflow elicited by nerve stimulation were studied in the perfused cat's spleen, at different calcium concentrations in the perfusion medium: 0‐26, 0‐65 and 2‐6 mve stimulation and in the overflow of the transmitter. PGE2 was more effective in reducing transmitter overflow at 5 than at 30 Hz. 3. Indomethacin, 14‐0 muM, prevented the release of PGE‐like material in the venous effluent of the spleen elicited by either nerve stimulation or by exogenous noradrenaline. 4. During exposure to 14‐0 muM indomethacin there was no increase in responses to nerve stimulation or in the overflow of noradrenaline elicited by nerve stimulation at 5 or at 30 Hz. 5. Similar results to those obtained with exogenous PGE2 and with indomethacin in the presence of 2‐6 mM calcium, were observed when the experiments were carried out in the presence of either 0‐65 or 0‐26 mM calcium. 6. In the presence of the alpha‐adrenoceptor blocking agents, phenoxybenzamine (2‐9 muM) or phentolamine (3‐1 muM), the increase in transmitter overflow obtained during stimulation was 6‐5 and 8‐3‐fold respectively. 7. Since inhibition of the synthesis of PGE did not increase transmitter overflow during nerve stimulation, it appears that the proposed negative feed‐back mechanism mediated by endogenous prostaglandins does not play an important physiological role in the regulation of adrenergic neurotransmission in the cat spleen. In this tissue the major endogenous negative feed‐back regulatory mechanism is triggered by the neurotransmitter through the activation of prejunctional alpha‐adrenoceptors.
The interaction of pH and divalent cations at the neuromuscular junction.
Authors: Landau E M , Nachshen D A
Published: December 2014

1. 1. The effects of acidic pH on transmitter release were studied at the frog neuromuscular junction, using intracellular recording techniques. 2. Acid pH reduced the amplitude of the end‐plate potentials (e.p.p.s) and accelerated the frequency of the miniature e.p.p.s(m.e.p.p.s). 3. At pH 6‐0 the m.e.p.p. frequency was on the average 2‐5 times greater than at pH 7‐4. This multiplication was independent of the divalent ion concentration of the medium over a large range. 4. Reduction of the e.p.p. amplitude at low pH was the result of a decrease in m, the number of quanta of transmitter liberated by the nerve impulse. 5. The effect of low pH on m was blocked by high concentrations of Mg2+ and by lower concentrations of Mn2+ ions. This occlusion was found even when the total concentration of divalents in the bathing solution was kept constant. 6. These results indicated that H+ and Mn2+ ions bind to an acidic site which regulates Ca‐mediated release of acetylcholine (ACh). The acid dissociation constant (KH) was determined using both a kinetic and a surface charge model. The pKa of the site calculated from the kinetic model was 5‐7, while a pKa of 3‐6 was obtained from the surface charge model. 7. It is suggested that protonation of the acidic site mentioned above reduces evoked transmitter release by blocking the influx of Ca into the nerve terminal following the nerve action potential.
Some effects of 5‐hydroxytryptamine, dopamine and noradrenaline on neurones in the submucous plexus of guinea‐pig small intestine.
Authors: Hirst G D , Silinsky E M
Published: December 2014

1. Responses to the iontophoretic application of 5‐hydroxytryptamine (5‐HT), dopamine and noradrenaline were examined in neurones of the submucous plexus of guinea‐pig small intestine. 2. Every neurone was excited by 5‐HT. 3. In a proportion of cells, dopamine or noradrenaline caused an increase in membrane potential. This response was only observed in cells which received in inhibitory innervation. The responses closely resembled inhibitory synaptic potentials evoked by transmural stimulation. 4. Both inhibitory synaptic potentials and inhibitory responses to dopamine and noradrenaline were blocked by methysergide. 5. It seems possible that these two catecholamines may interact with similar receptors to those activated by inhibitory transmitter.
Functional and structural changes in mammalian sympathetic neurones following interruption of their axons.
Authors: Purves D
Published: December 2014

The effects of interrupting the axons of principal neurones in the superior cervical ganglion of adult guinea‐pigs were studied by means of intracellular recording, and light and electron microscopy. 1. Within 72 hr of axon interruption, the amplitude of exitatory postsynaptic potentials potentials (e.p.s.p.s) recorded in principal neurons in response to maximal preganglionic stimulation declined. E.p.s.p.s were maximally reduced (by more than 70% on average) 4‐7 days following interruption, and failed to bring many cells to threshold. E.p.s.p.s. recorded in nearby neurones whose axons remained intact were unaffected. 2. In ganglia in which axon interruption was achieved by means of nerve crush (thus allowing prompt regeneration), mean e.p.s.p. amplitudes began to increase again after about 1‐2 weeks. One month after the initial injury many neurones had e.p.s.p.s of normal amplitude, and by 2 months affected neurones were indistinguishable from control cells. Functional peripheral connexions were re‐established during the period of synaptic recovery. 3. The mean number of synapses identified electron microscopically in ganglia in which all the major efferent branches had been crushed decreased by 65‐70% in parallel with synaptic depression measured by intracellular recording. However synapse counts did not return to normal levels even after 3 months. 4. During the period of maximum synaptic depression, numerous abnormal profiles which contained accumulations of vesicular and tubular organelles, vesicles, and mitochondria were observed in electron microscopic sections. Injection of horseradish peroxidase into affected neurones demonstrated dendritic swelling which probably correspond to these profiles. 5. Little or no difference was found in the electrical properties of normal neurones and neurones whose axons had been interrupted 4‐7 days previously. However, the mean amplitude of spontaneously occurring synaptic potentials was reduced, and the amplitude distribution was shifted. This abnormality of the synapses which remain on affected neurones also contributes to synaptic depression. 6. Counts of neurones in normal and experimental ganglia showed that approximately half the principal cells died 1‐5 weeks after crushing the major efferent brances. This finding presumably explains the failure of synapse counts to return to control levels after recovery. 7. If axons were prevented from growing back to their target organ by chronic ligation, surviving neurones whose axons were enclosed by the ligature did not generally recover normal synaptic function. Following ligation, most affected cells died within a month. 8. Thus the integrity of a principal cell's axon is necessary for the maintenance of preganglionic synaptic contacts, and ultimately for neuronal survival. The basis of neuronal recovery from the effects of axon interruption appears to be some aspect of regeneration to the peripheral target.
Differentiation of motoneurones and skeletal muscles in kittens.
Authors: Huizar P , Kuno M , Miyata Y
Published: December 2014

1. Isometric contractions of the medial gastrocnemius (fast switch) and soleus (slow twitch) muscles were recorded in kittens ranging in age from 3 to 112 days, as well as in adult cats. 2. It was confirmed that the speed of contraction of the gastrocnemius muscle becomes progressively faster during the first few weeks after birth, whereas contraction times of the soleus muscle show little changes or a slight prolongation during the period of post‐natal development. 3. The properties of gastrocnemius (fast alpha) and soleus (slow alpha) motoneurons were examined with intracellular electrodes in kittens at three different stages; 16‐20, 61‐71 and 100‐112 days in age. 4. The axonal conduction velocities of both gastrocnemius and soleus motoneurones increased monotonically throughout the period of development and showed no correlation with post‐natal changes in contraction times of the innervated muscles. 5. The duration of after‐hyperpolarization in soleus motoneurones became progressively longer with age, while that in gastrocnemius motoneurones remained virtually unchanged during development. 6. The relation between the duration of after‐hyperpolarization and the axonal conduction velocity in kitten motoneurones was similar to that observed in axotomized motoneurones of adult cats. 7. It is suggested that fast and slow alpha motoneurones show postnatal differentiation in terms of the duration of after‐hyperpolarization and that axotomy leads to 'dedifferentiation' of the motoneurone properties. 8. Post‐natal changes in the contractile properties of skeletal muscles were independent of the changes in the duration of after‐hyperpolarization of the innervating motoneurones. However, it remains uncertain whether muscle differentiation is independent of the discharge pattern of the innervating motoneurones.
Neural systems responsible for the gastric secretion provoked by 2‐deoxy‐D‐glucose cytoglucopoenia.
Authors: Kadekaro M , Timo-Iaria C , Valle L E
Published: December 2014

1. The central structures responsible for the gastrosecretory effect of cytoglucopoenia caused by 2‐deoxy‐D‐glucose (2‐DG) were investigated in 105 cats prepared with chronic gastric fistulae and subjected to various experimental procedures. 2. Bilateral electrolytic lesion of the caudalmost two thirds of globus pallidus almost suppressed the secretory response and caused aphagia and adipsia. 3. Secretion in response to 2‐DG and feeding behaviour were entirely blocked after making a lesion in a large ventromedial area of the meso diencephalic transition comprising the ventral tegmental area of Tsai, the ventral tegmental decussation, the red nucleus, a ventral portion of the central grey matter, the interstitial nuclei of Darkschewitsch and of Cajal, the pre‐rubral fields, the reticular part of substantia nigra, the internal portion of the cerebral peduncle and the ventral part of the mesencephalic reticular formation. 4. Microinjection of 2‐DG in the medial forebrain bundle, at the level of the hypothalamus, caused intense gastric secretion, whereas the same procedure was totally ineffective when the caudalmost two thirds of the globus pallidus were stimulated. 5. Increasing doses of 2‐DG, systemically injected, restored the secretory response in volume and acid concentration and output after intercollicular transection of the brain stem. After the transection, secretion of pepsin was only slightly increased when large doses of 2‐DG were administered, thus suggesting a differential control of water, acid and pepsin secretion in response to cytoglucopoenia. 6. It is concluded that there are at least three reflex systems involved in gastric secretion due to cytoglucopoenia: (a) a reflex consisting of afferent and efferent pathways in the medial forebrain bundle area; (b) a reflex whose afferent side is from the hypothalamus and efferent side is from the globus pallidus; (c) a reflex with the afferent side probably originating in the liver and the efferent side in the lower brain stem. 7. The pathways involved in the first two arcs run along Nauta's limbic mid‐brain circuit. The three systems are possibly related to control of secretion and feeding behaviour.
Interactions of rod and cone signals in the mudpuppy retina.
Authors: Fain G L
Published: December 2014

Interactions between rod and cone signals in mudpuppy retinal neurones were investigated by intracellular recording. 2. The mudpuppy retina contains one kind of rod (lambda max = 525 nm) and one kind of cone (lambda max = 572 nm). The responses of receptors can be distinguished on the basis of their spectral sensitivities. 3. Rod and cone responses have different time courses of recovery and absolute sensitivities. Differences between receptor responses can be used to describe inputs to interneurones. 4. There are two spectral classes of horizontal cells: L‐type and C‐type. L‐type cells are hyperpolarized by rods and cones in varying proportion, with some cells receiving little rod input. C‐type cells are hyperpolarized by rods and depolarized by cones. 5. Bipolar cell receptive field centres receive input from cones or from rods and cones. There is no correlation between the spectral properties of centre responses and their polarity. 6. Antagonistic surrounds of bipolar cells show cone or rod and cone sensitivity. They are believed to be generated by the L‐type horizontal cells. 7. Some bipolar cells exhibit chromatic interactions between cone signals in the centre and rod signals in the surround, which resemble those observed between the signals of different spectral classes of cones in species known to possess colour discrimination. 8. Amacrine and on‐off ganglion cells have L‐type responses showing both rod and cone sensitivity. 9. It is proposed that interactions between rod and cone signals observed in mudpuppy also exist in primate retina and are at least partially responsible for certain psychophysical observations of rod‐cone interactions.
Loss of alpha‐bungarotoxin from junctional and extrajunctional acetylcholine receptors in rat diaphragm muscle in vivo and in organ culture.
Authors: Berg D K , Hall Z W
Published: December 2014

Acetylcholine (ACh) receptors in rat diaphragm muscle were blocked by intrathoracic injection of alpha‐bungarotoxin (alpha‐BuTx) or [125I]alpha‐bungarotoxin ([125I]alpha‐BuTx). The stability in vivo of the toxin‐receptor complex formed by receptors in normal muscles and receptors in extrajunctional regions of denervated muscles was compared. Toxin was lost from junctional regions of normal muscles with a half‐time of approximately 6 days. The loss of toxin was accompanied by a corresponding increase in the number of free toxin‐binding sites. In contrast, 65% of the toxin bound to extrajunctional regions of denervated muscle was lost in 24 hr. 2. In a second series of experiments, animals were injected with [125I]alpha‐BuTx and the muscle subsequently cultured for 24 hr. Loss of toxin again occurred more rapidly from extrajunctional receptors than from junctional receptors. The loss from extrajunctional receptors was described by a single first‐order rate constant whose corresponding half‐time was 8‐11 hr. Loss was almost completely blocked by sodium cyanide and dinitrophenol and was inhibited by puromycin and cycloheximide. The radioactivity recovered in the medium was largely monoiodotyrosine. These results are consistent with the hypothesis that toxin loss reflects intracellular degradation of toxin‐receptor complex. 3. Neonatal rats were injected with [125I]alpha‐BuTx and the diaphragms cultured. Radioactive toxin was lost rapidly from extrajunctional regions of muscle and more slowly from regions containing end‐plates. 4. These results could be explained by a difference in turnover rates for junctional and extrajunctional receptors.
The voltage dependence of membrane capacity.
Authors: Adrian R H , Almers W
Published: December 2014

1. Membrane capacity of sartorius muscle fibres has been measured at membrane potentials between ‐200 and +50 mV. Within this potential range the capacity is not independent of potential. Dielectric saturation is present at large negative and at positive internal potentials, indicating the presence in the membrane of permanent dipoles or movable charges. 2. In normally polarized fibres there is a sharp peak in the capacity‐potential relation of about ‐50 mV; the capacity at this peak is 50% larger than the capacity at ‐90 mV. 3. In depolarized fibres this sharp peak of capacity is not present. Over the range ‐200 to +50 mV the capacity variation is about 10% with a broad maximum at about ‐80 mV. 4. The dielectric behaviour of muscle membrane is most simply explained by postulating two species of permanent dipoles or mobile charges: Charge 1 present in normally polarized fibres, but neutralized or immobilized in depolarized fibres; Charge 2 present in both polarized and depolarized fibres. The distribution of Charge 1 is more steeply voltage‐dependent than is the distribution of Charge 2. 5. Movement of Charge 1 from one fully saturated configuration to the other involves a charge transfer across the membrane of between 20 and 30 nC/muF. Movement of Charge 2 in depolarized fibres requires a similar transfer of charge.
The effects of corticosterone and cortisone on the uptake of polyvinyl pyrrolidone and the transmission of immunoglobulin G by the small intestine in young rats.
Authors: Morris B , Morris R
Published: December 2014

1. The distribution of polyvinyl pyrrolidone along the intestinal lumen and in the intestinal wall, following oral administration to normal and corticosterone treated rats, was found to be extremely variable. Valid comparisons between the two groups of animals could not be made using this technique. 2. Three, 4 and 5 days after corticosterone treatment there was no significant change in the uptake of 125I‐labelled polyvinyl pyrrolidone from standard doses injected into ligated segments of the distal small intestine; nor did the treatment induce precocious replacement of the absorptive cells in this region. Cortisone induced precocious cell replacement, a process which took up to 4 days to complete, and also led to a marked reduction in the uptake of 125I‐labelled polyvinyl pyrrolidone from ligated segments of the distal intestine. 3. Three days after treatment with corticosterone (5 mg I.P. at 12 days) there was a marked reduction of labelled immunoglobulin G transport into the blood. Four and 5 days after treatment there was some recovery of the immunoglobulin G transport function. Three days after treatment with cortisone (5 mg I.P. at 12 days) there was closure of the gut to labelled immunoglobulin G. 4. The relevance of these results to antibody transmission and the termination of immunoglobulin transport is discussed.
The acetylcholine sensitivity of the surface membrane of multiply‐innervated parasympathetic ganglion cells in the mudpuppy before and after partial denervation.
Authors: Roper S
Published: December 2014

1. The surface chemosensitivity to iontophoretically applied acetylcholine (ACh) of single nerve cells in the cardiac ganglion of the mudpuppy was examined. 2. Some synapses on the neurones can be recognized in the living preparation with differential interference contrast optics. Identified synaptic regions of the ganglion cells were more sensitive to ACh than were other areas. The mean sensitivity of synaptic areas was 509 mV/nC, but that of random spots on the cell surface (which were mainly non‐synaptic) was only 190 mV/nC. The mean rise time of ACh responses at synapses was 23 msec and at random spots was 36 msec. These data suggest that the density of ACh receptors is highest under the synapses on the post‐synaptic membrane. 3. When some, but not all, of the presynaptic terminals on the ganglion cells are destroyed by cutting the vagus nerve, the sensitivity of the entire surface membrane to applied ACh increases. This increase in sensitivity reaches a maximum about 4‐6 weeks after the operation. 4. Synaptic transmission at excitatory collateral synapses which remain after vagal degeneration is not altered by this hypersensitivity. 5. Neurones from ganglia which have been isolated and maintained in organ culture also become hypersensitive to applied ACh. this heightened chemosensitivity deveoops much faster in vitro; hypersensitivity in cultured ganglia becomes manifest within 4‐5 days, in contrast with 4‐6 weeks after vagus degeneration in vivo.
Stimulus‐secretion coupling processes in brain: analysis of noradrenaline and gamma‐aminobutyric acid release.
Authors: Cotman C W , Haycock J W , White W F
Published: December 2014

1. Brain synaptosomal fractions released both endogenous and exogenously loaded noradrenaline and gamma‐aminobutyric acid (GABA) in response to calcium. Elevation of magnesium concentrations in the release media decreased the calcium‐dependent release. 2. The release of noradrenaline and GABA occurred within 250 msec following the application of calcium. Following the initial response to calcium, release progressively decreased with continued application of calcium. GABA release declined more rapidly than noradrenaline release, consistent with a noradrenaline distribution having greater accessibility to the release process. 3. Sodium was required for the loading of noradrenaline and GABA into pools released by calcium. On the other hand, the presence of sodoium was not required for release from previously loaded pools. 4. Microsomal fractions did not exhibit calcium‐dependent release of noradrenaline or GABA. Furthermore, exogenously loaded lysine was not released from synaptosomal fractions in response to calcium. 5. Barium and strontium, but not magnesium, stimulated noradrenaline and GABA release in the absence of calcium. The ordering of alkaline earth efficacies was barium greater than strontium greater than calcium. 6. Manganese inhibited calcium‐dependent release of noradrenaline and GABA to a greater extent than magnesium. 7. Release, in response to 1 mM calcium, increased linearly with the log. [K+]0, suggesting that a voltage‐dependent calcium inophore limits release. The slope of release vs. log. [K+]0 was greater for noradrenaline than for GABA. 8. For a given [K+]0 less than 55 mM, increases in external calcium concentration above 1 mM increased noradrenaline release but decreased GABA release. These data suggest that calcium can decrease its own permeation and that differences in the release process may exist for different neurotransmitters. 9. In the presence of the artificial calcium ionophore, A23187, both noradrenaline and GABA release increased linearly with the log. [Ca2+]0. The slope for noradrenaline release was greater than that for GABA release. 10. Stimulus‐secretion coupling in brain is suggested to be regulated at the level of a voltage dependent calcium permeation mechanism. However, basic differences in the interaction of calcium with the release process may exist between the noradrenaline and GABA systems.
Relationship between initial chemical reactions and oxidative recovery metabolism for single isometric contractions of frog sartorius at 0 degrees C.
Authors: Kushmerick M J , Paul R J
Published: December 2014

1. Measurements of intitial chemical changes and recovery oxygen consumption (deltaO2) were made in unpoisoned aerobic frog sartorius muscles at 0 degrees C to provide independent measures of the chemical energy used for isometric tetani of various durations. 2. DeltaO2 was measured polarographically and increased in a curvilinear fashion with stimulus duration. For stimulations longer than 4 sec deltaO2 was a linear function of the tension‐time integral. 3. Measurements of the changes in the content of phosphorylcreatine, 'free' creatine and inorganic phosphate were made in muscles rapidly frozen during a tetanus. The average of these quantities, delta approximately P, was used to measure the initial 'high energy' phosphate utilization. No break‐down of 'high‐energy' phosphate compounds was detected up to 200 sec after relaxation of tension. Changes in the content of ATP were not observed except for a small decrease (‐0‐25+/‐0‐1 mumole/g) in muscles tetanized for 1 sec. 4. Delta approximately P also increase curvilinearly with tetanus duration and, for tetanic durations greater than 4 sec, was a linear function of the tension‐time integral. 5. Both deltaO2 and delta approximately P were quantitatively related by a constant scaling factor of about 4‐3 (delta approximately P/deltaO2) throughout the range of tetanic durations studied. The constancy of this ratio.provides evidence against the hypothesis that a significant 'missing reaction' provides energy during any one portion of the tetanus. Several hypothesis may account for the numerical value of the ration delta approximately P/deltaO2.
The temporal and steady‐state relationships between activation of the sodium conductance and movement of the gating particles in the squid giant axon.
Authors: Keynes R D , Rojas E
Published: December 2014

1. Comparisons were made between the kinetics and steady‐state properties of the sodium conductance changes and of the sodium gating currents, in the squid giant axon perfused with caesium fluoride and maintained at a high membrane holding potential. The conductance measurements were made with reduced external sodium and as much electrical compensation as possible, in order to minimize errors caused by the series resistance. 2. After an initial delay of 10‐150 musec whose size was a function of the holding potential and pulse amplitude, the conductance rise on depolarization followed cube law kinetics. 3. Values of the time constant taum, as defined by Hodgkin & Huxley (1952b), were determined for membrane potentials ranging between ‐140 and +70 mV. They lay on a nearly symmetrical bell‐shaped curve with maximum (at 6‐3 degrees C) of just under 500 musec at ‐36 mV. 4. Values of the gating current time constant tau(V) were determined over the same potential range, and found to lie on a very similar bell‐shaped curve. A computed least‐squares best fit gave the maximum as 460 musec, also falling at about ‐36 mV. 5. The midpoint of the minfinity curve lay at ‐34 mV, and its slope at this point was 0‐0139 mV‐1. Another series of measurements on intact axons gave a midpotential of ‐25 mV. In the perfused axons the state of the membrane was better described by the constant field equation than by gNa. Recalculation of minfinity from PNa shifted the curve about 15 mV in a positive direction.