bluuebunny/crossref_metadata_2025_split huggingface dataset:
Supporting effects of myoepithelial cells in submandibular glands of dogs when acting against increased intraluminal pressure
Authors: Emmelin N. , Garrett J. R. , Gjörstrup P. 
Published: December 2014

1. In dogs under chloralose‐urethane anaesthesia secretion from the submandibular gland was recorded with the outflow at gland level and at heights of up to 50 cm above the gland.2. With the outflow level increased, secretion elicited by sympathetic nerve stimulation was far better maintained before than after injection of the α‐adrenoceptor blocking agent dihydroergotamine.3. When the outflow level was raised while no secretion occurred, fluid flowed into the gland. Part of this amount was returned on lowering the outflow to gland level. This volume was assumed to have been accommodated in the distended luminal system, whereas some fluid was obviously lost into the gland tissues.4. Both these fractions of the fluid flowing into the gland when the outflow level was high could be reduced by injecting the α‐receptor agonist phenylephrine. Bradykinin, which like phenylephrine is known to contract salivary myoepithelial cells, had the same effect on the two inflow volumes.5. It is concluded that myoepithelial contraction reduced the distensibility of the luminal system and in addition supported the acini, thereby diminishing backflow into the glandular tissues and enabling the gland to discharge saliva against a high pressure.6. Morphologically it was found that in resting glands PAS‐positive saliva was displaced from the ductal system when the outflow cannula was raised, but it was preserved in the lumina under similar conditions when the myoepithelial cells were being stimulated by phenylephrine or bradykinin.7. Although sympathetic secretion could be maintained against a head of pressure, so long as it was accompanied by myoepithelial contraction, the increased force caused by the secretion led to disruptive damage of striated ducts which are the first part of the luminal system not supported by myoepithelial cells.8. The morphological findings reinforce the belief that contraction of myoepithelial cells gives active support to the underlying parenchyma.
Inhibition of cuneate neurones: its afferent source and influence on dynamically sensitive ‘tactile’ neurones
Authors: Bystrzycka E. , Nail B. S. , Rowe Mark 
Published: December 2014

1. Responses were recorded in decereberate, unanaesthetized cats from individual cuneate neurones in order to determine firstly, the afferent sources of inhibition on cuneate neurones and secondly, the influence of afferent‐induced inhibition on those response features of dynamically sensitive tactile neurones which determine their capacity to code information about parameters of tactile stimuli.2. For all cuneate neurones which displayed afferent‐induced inhibition from areas surrounding or within their excitatory receptive field (71% of the sample) it was consistently found that 300 Hz vibration at low amplitudes (< 25‐50 μm) which selectively engages Pacinian corpuscles was an effective source of inhibition. In contrast, steady indentation which activates slowly adapting tactile afferents was quite ineffective, as was low frequency vibration (30 Hz) at amplitudes of < 50‐100 μm. The latter stimulus can be used to engage rapidly adapting receptors either within glabrous skin (presumed to be Meissners corpuscles) or in association with hair follicles. It is concluded that afferents from Pacinian corpuscles are the dominant or exclusive source of afferent‐induced inhibition of cuneate neurones.3. For dynamically sensitive neurones responsive to low frequency cutaneous vibration (30 Hz) there was a reduction in the slope of stimulus—response relations with afferent‐induced inhibition, but no expansion of the range of stimulus amplitudes over which the neurone responded.4. The influence of afferent‐induced inhibition on the phase‐locking of impulse activity to a cutaneous vibratory wave form was examined by constructing post‐stimulus time histograms and cycle histograms. Measures of dispersion of impulse activity around the preferred point of firing in the vibratory waveform indicated that the capacity of individual cuneate neurones to code information about the frequency of the cutaneous vibration was not systematically changed in the presence of afferent‐induced inhibition.
Ia afferent activity during a variety of voluntary movements in the cat
Authors: Prochazka A. , Westerman R. A. , Ziccone S. P. 
Published: December 2014

1. Implanted dorsal root electrodes were used to record discharge trains of single spindle primary afferents (Ia's) of the cat's hind limb during different types of movement.2. The length of the ipsilateral ankle extensors was continuously monitored by an implanted length gauge. Length changes occurring during active stepping were subsequently passively reproduced during brief anaesthesia.3. A comparison of the Ia responses in active and simulated step cycles revealed that moderate fusimotor drive to ankle extensor spindles probably occurred mainly, if not exclusively, during the E1, E2 and E3 phases of active stepping.4. A temporal advance in the Ia response to passive stretching in the F‐phase was attributed to the after‐effects of fusimotor activity in the extension phases.5. Light thrust applied to the animal's back evoked a potent fusimotor response. This load compensation effect may provide an explanation for the apparently higher degree of α‐γ co‐activation seen in the mesencephalic locomotor preparation.6. Ankle extensor Ia discharge decreased during falls, despite an increase in extensor e.m.g. This is seen as a clear example of independent α and γ control.7. Placing reactions during walking were consistent with the notion that cutaneous inputs dominate over proprioceptive inputs in these movements.8. α and Ia discharge during paw‐shaking showed many of the characteristics of that in decerebrate and spastic clonus. The present results suggest that movements resembling clonus may be part of the animal's normal repertoire.9. Isometric co‐contraction of agonists and antagonists was found to involve α‐γ co‐activation.10. Hamstring Ia discharge behaviour during stepping further highlighted the increases in firing rate which normally occur during passive muscle stretching in ‘pre‐programmed’ movements.
Sensory deprivation during development decreases the responsiveness of cricket giant interneurones
Authors: Matsumoto S. G. , Murphey R. K. 
Published: December 2014

1. The effect sensory deprivation, early in development, has on the adult response properties of identified neurones was studied in the abdominal nervous system of the cricket Acheta domesticus.2. Neural activity in the cercal‐to‐giant interneurone system was lowered by blocking the movement of the mechanosensitive hairs, located on each cercus, with a facial cleansing cream.3. When specimens were treated unilaterally one of a pair of homologous neurones exhibited drastically altered response properties. The neurone which received its afferent input from the treated receptors was much less sensitive to tones. Its threshold was increased approximately 20 db with respect to its untreated homologue.4. Bilateral treatment lowered the responsiveness of both of the bilaterally homologous neurones.5. Increased levels of inhibition impinging on the treated neurones accounts for part of the altered responsiveness. The inhibitory pathway is activated by the untreated mechanoreceptors.6. Control experiments demonstrate that the sensory apparatus is not injured or modified by the treatment.7. The results suggest that normal development of some invertebrate neural pathways may be more dependent on experience during ontogeny than has previously been assumed.
The relation between surface tension and area in the alveolar lining film
Authors: Pattle R. E. 
Published: December 2014

1. The properties of the rat alveolar lining film have been studied by observing the behaviour in a hanging drop, under reduced or increased ambient pressure, of bubbles derived from the lung.2. When such a bubble, covered by a metastable film of surfactant, is made to shrink, the material displaced from the surface usually remains in a form in which it can be re‐adsorbed to the surface and retains its surpellic properties.3. When an excess of surfactant is available for adsorption to the surface of such a bubble in water, an increase in area to about 1.25 (ϕ) times the metastable area is both necessary and sufficient for additional adsorption to the surface to take place.4. No significant variation of the ratio ϕ with temperature between 22 and 37° C has been found.5. It is concluded that during quiet breathing (involving a twofold change in lung volume in the rat) the variation in alveolar surface area is less than 25%. This finding is compatible with the extant morphometric data, but not with any assumption that the surface area is proportional to the 2/3 power of the gas volume.6. The behaviour of the bubbles in blood serum is similar to that in water. In a 2% solution of the detergent Tween 80, further adsorption of surfactant to the bubble surface does not take place.7. The fact that bubbles obtained from the lung by instillation of a solution of Tween 80 have surfactant linings similar to those of bubbles obtained with water or saline demonstrates that the bubble lining layer consists of the original alveolar lining layer detached.8. When a metastable bubble is stretched, it sometimes behaves as if some or all of its surfactant had been lost from the surface. The causes of this are unknown.9. The amount of surfactant associated with metastable bubbles freshly squeezed from a fragment of lung varies from bubble to bubble; the amounts found have ranged from 1 to 4.5 times (mean, 2) that required to cover the original bubble area with a metastable film. This would be compatible with an alveolar lining film of very uneven thickness.10. The maximum surface tension reached in the early stages of expansion of a lung bubble from the metastable state is about 34 mN/m.
Quantitative analysis of the velocity characteristics of optokinetic nystagmus and optokinetic after‐nystagmus
Authors: Cohen Bernard , Matsuo Victor , Raphan Theodore 
Published: December 2014

1. Velocity characteristics of optokinetic nystagmus (OKN) and optokinetic after‐nystagmus (OKAN) induced by constant velocity full field rotation were studied in rhesus monkeys. A technique is described for estimating the dominant time constant of slow phase velocity curves and of monotonically changing data. Time constants obtained by this technique were used in formulating a model of the mechanism responsible for producing OKN and OKAN.2. Slow phase velocity of optokinetic nystagmus in response to steps in stimulus velocity was shown to be composed of two components, a rapid rise, followed by a slower rise to a steady‐state value. Peak values of OKN slow phase velocity increased linearly with increases in stimulus velocity to 180°/sec. Maximum slow phase eye velocities in the monkey are 2‐3 times as great as in humans.3. At the onset of OKAN, slow phase velocity falls by about 10‐20%, followed by a slower decline to zero. Peak OKAN slow phase velocities were linearly related to optokinetic stimulus velocities up to 90‐120°/sec. Above 120°/sec OKAN slow phase velocity saturated although OKN slow phase velocity continued to increase.4. The charge and discharge characteristics of OKAN were studied. The OKAN mechanism charged in 5‐10 sec and discharged over 20‐60 sec in darkness. The time constants of decay in OKAN slow phase velocity decreased as stimulus velocities increased. They also decreased on repeated testing. In several monkeys there was a consistent difference in the rate of decay of OKAN slow phase velocity to the right and left.5. Extended visual fixation discharged the activity responsible for producing OKAN. Short fixation times caused only a partial discharge of the OKAN mechanism. Following brief periods of fixation, OKAN resumed but with depressed slow phase velocities.6. A model based on a state realisation of a peak detector was formulated which approximately reproduces the salient characteristics of OKN and OKAN. This model predicts the three dominant characteristics of OKAN: (1) charge over 5‐7 sec, (2) slow discharge in darkness, and (3) rapid discharge with visual fixation. With the addition of direct fast forward pathways, it also correctly predicts the rapid and slow rise in OKN. We postulate that OKAN is produced by a central integrator which is also active during OKN. Presumably this integrator acts to maximize velocities during OKN and to smooth and stabilize ocular following during movement of the visual surround.
Separation of sodium and calcium currents in the somatic membrane of mollusc neurones. With an Appendix by Yu A. Shakhovalov
Authors: Kostyuk P. G. , Krishtal O. A. , Shakhovalov Yu A. 
Published: December 2014

1. Characteristics of the transmembrane ionic currents under controlled changes in ionic composition of extra‐ and intracellular medium were studied in isolated neurones from the ganglia of molluscs, Helix pomatia, Limnea stagnalis and Planorbis corneus. The neurones were investigated by a new technique which allows for dialysis of their interior and for clamping of the potential at the surface membrane without using micro‐electrodes.2. Replacement of K ions by Tris inside the neurones eliminated the outward K current so that the actual time course of the inward current could be measured. The latter was separated into two additive components, one of which was carried by Na ions and the other one by Ca ions.3. Both inward currents were unaltered by tetrodotoxin (TTX); however, Ca current could be separately blocked by externally applied Cd ions (Kd = 7·2 × 10−5
M) and by the use of fluoride as an intracellular anion.4. No reversal of Na inward current could be achieved in neurones dialysed with Na‐free solution, indicating the absence of outward current carrying ions through the corresponding channels. With 5 m
M‐Na inside the cell, the equilibrium potential was close to the value predicted by the Nernst equilibrium.5. A non‐specific outward current could be detected in K‐free cells at membrane potentials exceeding 20‐40 mV. Its time course was proportional to 1 — exp (—t/τns). Cd ions depressed this current. The presence of the non‐specific outward current made an exact measurement of the equilibrium potential for the Ca inward current impossible.6. The kinetics of Na inward currents could be described by m3h and those of the Ca current by m2h law. The corresponding values for Vm = 0 are: τm(Na) = 1·1 ± 0·5 msec, τm(Ca) = 2·4 ± 1·0 msec, τh(Na) = 7·9 ± 2·0 msec. The inactivation of Ca current included two first‐order kinetic processes with τh1 = 50 ± 10 msec and τh = 320 ± 30 msec.7. The data presented are considered to be a proof of the existence of separate systems of Na and Ca ion‐conducting channels in the nerve cell membrane.
Effects of calcium and calcium‐chelating agents on the inward and outward current in the membrane of mollusc neurones
Authors: Kostyuk P. G. , Krishtal O. A. 
Published: December 2014

1. Effects of internal and external Ca and Ca‐chelating agents, EGTA and EDTA on transmembrane ionic currents were studied in isolated, internally dialysed neurones from the molluscs, Helix pomatia and Limnea stagnalis.2. The possible pharmacological effect of internally applied EGTA was investigated on the background of constant free Ca concentration (5·3 × 10−9
M). EGTA had no effect on Ca and Na inward currents but considerably depressed the delayed K outward current. No effective removal of this action could be achieved by the elevation of intracellular free Ca.3. In the absence of divalent cations in the external medium, EGTA (as well as EDTA) applied either intra‐ or extracellularly caused the appearance of a very large Na inward current with kinetics similar to those of Ca inward current and with the reversal potential around 10 mV. Effective concentrations of chelating agents were 0·1 m
M (extracellular) and 1·0 m
M (intracellular).4. Increase in intracellular Ca in the absence of EGTA (by dialysis of the cell with Ca‐saturated solutions) did not produce any significant effect on the delayed K outward current. The small change observed in this current could be evaluated as a depression of maximum slope conductance and a shift to more negative membrane potential.5. Ca inward current has been found extremely sensitive to internal Ca. 5·8 × 10−8
M of internal free Ca produced its complete depression. This effect was reversible. Na inward current could be inhibited with 3·5 × 10−7
M intracellular Ca.
Capillary supply of the quadriceps femoris muscle of man: adaptive response to exercise
Authors: Andersen Per , Henriksson Jan 
Published: December 2014

1. Five subjects trained for 8 weeks on a bicycle ergometer for an average of 40 min/day, four times a week at a work load requiring 80% of the maximal oxygen uptake (V̇O2 max.). V̇O2 max. determinations were performed, and muscle biopsies from the quadriceps femoris muscle (vastus lateralis) were taken before, as well as repeatedly during, the training period. The muscle biopsies were histochemically stained for fibre‐types (myofibrillar ATPase) and capillaries (amylase‐PAS method), and analysed biochemically for succinate dehydrogenase and cytochrome oxidase activities.2. The training programme resulted in a 16% increase in V̇O2 max., a 20% increase in capillary density, a 20% increase in mean fibre area, and an approximately 40% increase in the activities of succinate dehydrogenase and cytochrome oxidase.3. The capillary supply to type I, IIA and IIB fibres, expressed as the mean number of capillaries in contact with each fibre‐type, relative to fibre‐type area, increased equally.4. The present study shows that endurance training constitutes a powerful stimulus for capillary proliferation in human skeletal muscle.
Continuous direct measurement of intracellular chloride and pH in frog skeletal muscle
Authors: Bolton T. B. , Vaughan-Jones R. D. 
Published: December 2014

1. Ion‐sensitive electrodes (made with a chloride‐sensitive ion‐exchange resin) were used to measure the internal chloride activity (aiCl) of frog sartorius fibres at 25° C.2. The internal pH (pHi) of other sartorius fibres was measured with a recessed tip pH‐sensitive electrode (made with pH‐sensitive glass).3. In normal bicarbonate‐free solution (containing 2·5 m
M potassium), the average chloride equilibrium potential, ECl (calculated from aiCl and the measured chloride activity of the external solution (aoCl) was 87·7 ± 1·7 mV (mean ±
S.E.; n = 16) in fibres where the average membrane potential, Em, was 88·3 ± 1·5 mV (mean ±
S.E.; n = 16). In experiments where aiCl was varied between about 1 and 10 m
M (which corresponds to values of Em between about ‐105 and ‐50 mV) ECl was within 1‐3 mV of Em at equilibrium. These measurements of aiCl were obtained from the potential difference between the chloride‐sensitive electrode and an intracellular indifferent micro‐electrode filled with potassium chloride. If a potassium sulphate‐filled indifferent micro‐electrode was used, then values of aiCl below about 5 m
M were erroneously high, probably due to interference from other sarcoplasmic ions at the indifferent electrode.4. In solutions containing 15 m
M bicarbonate and gassed with 5% CO2, pHi was 6·9, corresponding to an internal bicarbonate concentration of 7·6 m
M. ECl measured in this solution was some 4 mV positive to Em. Most of the difference between ECl and Em could be ascribed to interference by sarcoplasmic bicarbonate on the basis of selectivity measurements of chloride against bicarbonate made on the ion‐exchange resin in the relevant range of aCl.5. If bicarbonate/CO2 in the external solution was replaced by
HEPES/pure O2 at constant pH, then pHi rose from 6·88 ± 0·02 (mean ±
S.E.) to 7·05 ± 0·02. A change in external pH of 1 unit caused pHi to change by about 0·02 unit and the intracellular buffering power was calculated to be about 35.6. In solution made hypertonic by the addition of sucrose, Em changed little or depolarized and ECl and Em remained close. In contrast, in solution made hypertonic by the addition of solid sodium chloride (high‐chloride solution) ECl became negative to Em. Conversely in low chloride solution ECl became positive to Em.7. When the chloride permeability (PCl) was reduced by the use of acid solution, ECl moved positive to Em indicating an accumulation of internal chloride. When PCl was increased again by returning to more alkaline solution, Em depolarized to ECl.8. The results are consistent with the existence of a small, active movement of chloride, the effects of which are normally obscured by large passive movements of chloride when PCl is large.
A ‘late supernormal period’ in the recovery of excitability following an action potential in muscle spindle and tendon organ receptors
Authors: Gregory J. E. , Harvey R. J. , Proske U. 
Published: December 2014

1. Discharge patterns have been recorded from five types of stretch receptor; frog muscle spindles, lizard tendon organs, cat soleus tendon organs and primary and secondary endings of cat soleus muscle spindles.2. The fully adapted discharge of each type of receptor is irregular, especially for frog spindles and primary endings of cat spindles as compared with the other three types (the ‘regularly firing’ receptors). Frog spindles and some cat spindle primary endings would maintain a discharge at very low mean rates (1/sec or less) while the remaining receptors would stop suddenly, as soon as their rate of discharge fell below a critical value characteristic for each individual ending.3. This pattern of discharge suggests that there is a peak in the excitability of ‘regularly firing’ receptors at a time following a preceding impulse, which corresponds to the intervals between impulses at each particular receptor's slowest rate of maintained firing, and that the excitability subsequently falls again. Primary endings of cat muscle spindles also showed some evidence of such a ‘late supernormal period’, but frog spindles did not.4. Direct evidence for the ‘late supernormal period’ was obtained from experiments in which a maintained discharge was restarted by an antidromic action potential in a receptor which had stopped firing, and to which had been applied a stretch just too small to restart the discharge.5. It is shown in an Appendix that a model receptor in which the recovery of excitability following an impulse has a hyperbolic time course, and in which Gaussian distributed noise is superimposed on the generator potential, can have a discharge pattern very closely resembling that of a frog spindle (cf. Buller, 1965).6. After addition of a late supernormal period to the model, its discharge pattern could mimic closely that of a lizard or cat tendon organ, or of a secondary ending of a cat spindle.