bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synaptic actions of peripheral nerve impulses upon Deiters neurones via the climbing fibre afferents
Authors: Allen G. I. , Sabah N. H. , Toyama K. 
Published: December 2014

1. The cerebellar integration of sensory inputs to Deiters neurones was studied in cats under Nembutal anaesthesia.2. Stimulation of peripheral nerves produced in the Deiters neurones a sequence of an initial excitatory post‐synaptic potential (e.p.s.p.) and a later inhibitory post‐synaptic potential (i.p.s.p.), or a relatively small e.p.s.p.3. The Deiters neurones were classified as forelimb (FL)‐ or hind limb (HL)‐type cells according to the location of the most effective peripheral nerve. In the FL cells stimulation of the forelimb nerves produced the e.p.s.p.—i.p.s.p. sequence (dominant response), while stimulation of the hind limb nerves was ineffective or produced the small e.p.s.p. (non‐dominant response). In contrast, in the HL cells the non‐dominant response was evoked from the forelimb nerves, and the dominant response from the hind limb nerves.4. The stimulus intensity—response relation indicates that Group I and II muscle afferents and low and high threshold cutaneous afferents contribute to the dominant and non‐dominant responses.5. Antidromic identification of these Deiters neurones revealed that 90% of the HL cells and 85% of the FL cells project to the lumbo‐sacral and cervico‐thoracic segments of the spinal cord, respectively, while 10% of the HL cells and 15% of the FL cells innervate the cervico‐thoracic and lumbo‐sacral segments, respectively.6. The mean latency of the e.p.s.p. evoked from the forelimb nerves was 14 msec in the FL cells and 13 msec in the HL cells, and the latency of the e.p.s.p. evoked from the hind limb nerves was 17 msec in the FL cells and 18 msec in the HL cells. The later i.p.s.p. regularly followed the onset of the e.p.s.p. with a delay of 3–5 msec.7. The dominant and non‐dominant responses in both types of cells exhibited the following three characteristic features: (i) a strong depression after conditioning stimulation of the inferior olive, (ii) an increase of the inferior olivary excitability during the responses, and (iii) a striking frequency depression with stimulation at relatively low frequency (5–10/sec).8. Consequently it was concluded that all of the responses were produced through the climbing fibres originating from the inferior olive, the i.p.s.p.s due to inhibition from Purkyně cells activated by the climbing fibres and the e.p.s.p.s due to excitation from the collaterals of the climbing fibres.
Potential‐dependent membrane current during the active transport of ions in snail neurones
Authors: Kostyuk P. G. , Krishtal O. A. , Pidoplichko V. I. 
Published: December 2014

1. The membrane current caused by the iontophoretic injection of sodium into giant neurones of the snail Helix pomatia was investigated under a long lasting voltage clamp. The inhibition of this current by ouabain (10−4 M) and by cooling to + 7° C confirmed its link with the active transport of ions. Therefore this current is called the pump current.2. Over the range of membrane potential −40 to −100 mV the changes in the steady current—voltage curves caused by the pump current development were investigated. The pump current was found to be potential‐dependent. It decreased with increasing hyperpolarization of the neurone.3. With large hyperpolarizations the current—voltage curves obtained before the sodium injection and after eliciting the pump current coincided with each other. An increase in the membrane conductance was observed over the range of membrane potential corresponding to the pump current display.4. The applied sodium injections did not cause any marked changes in the passive permeability of the membrane. This fact made it possible to measure the charge transferred across the membrane during operation of the pump current. Unlike previous data, the ratio of this value to the charge used to inject sodium into the neurone appeared to be a variable.5. When the preparation was cooled to + 11° C, and also during the first few minutes after the application of a potassium‐free solution, both the pump current and the membrane potential at which it disappeared could increase.6. The pump current measurements during a number of transitions from one fixed level of the membrane potential to another showed that the current did not depend upon the potential at which it developed before each transition.7. The data presented allow the suggestion that the potential dependence of the pump current is determined by the changes in the rate of active transport of potassium, while the rate of active transport of sodium remains constant.
Mechanisms of ion transport across the choroid plexus
Authors: Wright Ernest M. 
Published: December 2014

1. Mechanisms of ion transport across the choroidal epithelium were investigated using an in vitro preparation of the frog choroid plexus.2. Sodium was actively transported across the plexus from the vascular to the ventricular surface by an ouabain sensitive electrically silent pump. As in other epithelial membranes the rate of sodium transport was stimulated by the presence of bicarbonate ions in the Ringer solutions. Chloride and bicarbonate ions accompany the net flux of sodium across this tissue.3. Some experiments suggest that potassium is actively transported from the ventricular to the serosal surface, and that the rate of transport is a function of the extracellular potassium concentration.4. No evidence was obtained to suggest that calcium is actively transported across this tissue in either direction.5. Diamox, ethoxyzolamide, pitocin, pitressin, hydrocortisone, amiloride, spironolactone and anoxia all failed to influence sodium transport.6. The sequence of passive ion permeation across the plexus was PRb ∼ PK > PCs ∼ PNa ∼ PCl ∼ PHCO3 > PLi as deduced from diffusion potential measurements. At least for Na, K and Cl there was a good correlation between the permeability coefficients derived from unidirectional flux measurements and from electrical parameters. This indicates that exchange diffusion is unimportant as a mechanism for passive ion transport.7. The instantaneous current—voltage curves were linear in both symmetrical and asymmetrical salt solutions and the choroid plexus conductance was found to be directly proportional to the external salt concentration. These and other lines of evidence suggest that the major route of passive ion permeation across this epithelium is via the tight junction route and not through the cell interior.8. These results are discussed in relation to the in vivo studies of c.s.f. secretion and the mechanisms of active and passive ion transport across other epithelial membranes such as the gall‐bladder, intestine and renal proximal tubule.
The efflux of magnesium from single crustacean muscle fibres
Authors: Ashley C. C. , Ellory J. C. 
Published: December 2014

1. In the large single muscle fibres from the barnacle Balanus nubilus, the total fibre Mg concentration was estimated as 15·1 m‐mole/kg wet wt., of which about 3–3·5 m‐mole/kg wet wt. was extracellular. The diffusible Mg, measured by internal sampling, was 11·5 m‐mole/kg wet wt., of which at least half may be complexed to larger diffusible molecules. The free ionized Mg level was estimated as < 5 m‐mole/kg wet wt.2. The loss of [28Mg]MgCl2 from both Maia and Balanus muscle fibres following axial micro‐injection approximated to first‐order kinetics. The maximum rate constant for the loss was 1·51 ± 0·20 (
S.E.) × 10−5 sec−1 for Balanus (sixty‐seven fibres) and 1·06 ± 0·46 (
S.E.) × 10−5 sec−1 for Maia (seven fibres) at 20–25° C.3. The calculated Mg efflux was in the range 6–12 p‐mole/cm2.sec based on this rate constant, assuming isotopic equilibration internally and that the surface area of the fibres approximated to that of a simple cylinder. If account was taken of the area of the cleft system the efflux was reduced by about fifteen times.4. The diffusion coefficient for injected 28Mg was estimated as 2–3 × 10−6 cm2 sec−1, about half the value in free solution. Injections of 2
M‐MgCl2 or 200 m
M‐EDTA subsequent to the injection of the isotope caused about a 30% reduction in the tracer efflux.5. External application of salines containing 100 m
M‐Ca or Mg caused a rapid but reversible inhibition of the magnesium efflux. Similar effects were observed with salines containing 32 m
M‐Co or Mn chlorides or 1–2 m
M‐La or Gd chlorides. Polyarginine (200 μg/ml.) had no effect.6. The Mg efflux had a Q10 of 3–4 over the temperature range of about 5–20° C. It was irreversibly inhibited by the sulphydryl reagent NEM (1 m
M), but PCMBS (0·2–2 m
M) had no effect. Contractile agents (5 m
M caffeine or 200 m
M‐K salines) and a variety of inhibitors of ion movement or active transport had no appreciable effect on the Mg efflux. Lowering the pH of the saline from 7 to 5 produced a 70% reduction in the efflux which was reversible over short periods of application.7. Replacement of external Na, but not Ca or Mg, with Li, choline or sucrose caused a rapid and partially reversible reduction of the Mg efflux, but increasing the internal Na by micro‐injection in zero Na salines had no consistent effect. It is suggested that the extrusion of Mg from these muscle cells is largely dependent upon the inward movement of Na.
Calcium dependence of ciliary activity in the oviduct of the salamander Necturus
Authors: Eckert Roger , Murakami Akira 
Published: December 2014

1. Ciliary activity in the oviduct of the mud puppy Necturus maculosus was monitored by a photometric technique in normal, decalcified, and Triton X‐extracted preparations to investigate the regulatory role of calcium ions.2. The frequency of ciliary beating in the isolated tissue ranged from 0 to 12 beats/sec. The frequency in any one group of cells underwent large cyclical variations with periods of 2 min or more.3. Frequency of beating reached a maximum and remained at a plateau upon addition of 1 m
M caffeine. Beating temporarily ceased upon removal of the caffeine.4. Ionophoretic injection of calcium ions into an active cell bathed in Ringer solution produced an increased rate of beating. In cells rendered quiescent by prior decalcification with EGTA, injected calcium rapidly restored ciliary activity.5. Epithelia extracted in Triton X‐100 were inactive until reactivated by addition of ATP and magnesium ions. The frequency of beating increased between 0·1 and 4·0 m
M ATP in 1 m
M magnesium, and between 0·2 and 2·5 m
M magnesium in 1 m
M ATP.6. The frequency of beating in the ATP‐reactivated, Triton‐extracted tissue was independent of the calcium ion concentration.7. Cells inactivated by decalcification were reactivated by injection of ATP or by extracellular ATP levels as low as 3 × 10−8
M.8. It is concluded that the frequency of beating depends directly on the concentration of the available energy source, presumably ATP, and that an indirect dependence of beating frequency on calcium concentration in the living tissue results from rate‐limiting effects of intracellular calcium on metabolic steps in pathways leading to ATP synthesis.
Vascular responses and noradrenaline overflows in the isolated blood‐perfused cat spleen: some effects of cocaine, normetanephrine and α‐blocking agents
Authors: Cripps Heather , Dearnaley D. P. 
Published: December 2014

1. Vascular responses and noradrenaline overflows have been studied in the isolated blood‐perfused cat spleen in response to electrical stimulation of the splenic nerve with trains of 200 supramaximal pulses at a frequency of 10 Hz given at 10 min intervals.2. In the absence of blocking agents the spleen gave well‐defined responses and a mean maximum overflow of 436 ± 96 pg noradrenaline per stimulus (n = 4) at the third train of stimuli.3. Cocaine (2 × 10−5
M) increased the response nearly threefold and raised the overflow to 840 ± 131 pg/stim (n = 4). At later stimulations the responses remained stable, but the overflows rose progressively to 1076 ± 51 pg/stim after five trains of stimuli.4. Normetanephrine (10−4
M) had no significant effect on response, but elevated the overflow to a mean maximum of 868 ± 169 pg/stim (n = 4).5. Cocaine (2 × 10−5
M) and normetanephrine (10−4
M) given together increased the response by a factor of 6·5 and raised the overflow to 1258 ± 247 pg/stim (n = 4).6. Hydergine (approx. 10−5
M) almost completely abolished the response and raised the overflow to 859 ± 173 pg/stim (n = 4).7. Cocaine (2 × 10−5
M), normetanephrine (10−4
M) and hydergine (approx. 10−5
M) given in combination abolished the response and raised the overflow to 4089 ± 1148 pg/stim (n = 4).8. Phenoxybenzamine (10−4
M) abolished the response and elevated the overflow to 4215 ± 738 pg/stim (n = 4).9. These results are interpreted in terms of selective and combined block of ‘uptake I’, ‘uptake II’ and α‐adrenergic receptors. Facilitation of transmitter release by α‐blocking drugs, and the possible existence of an uptake process associated with the α‐receptors are discussed.
Mobility and transport of magnesium in squid giant axons
Authors: Baker P. F. , Crawford A. C. 
Published: December 2014

1. The Mg content of axons obtained from Loligo forbesi averaged 6·4 ± 0·8 m‐mole/kg axoplasm.2. A small patch of radioactive 28Mg injected into an axon broadened considerably. A similar patch of 45Ca showed hardly any broadening. The self‐diffusion coefficient of Mg in axoplasm is about 2 × 10−6 cm2/sec which is at least twenty times greater than that of Ca.3. Under the influence of an applied electric field Mg migrated towards the cathode. Its mobility was about half of that of Mg in free solution. This suggests that the concentration of ionized Mg in squid axoplasm is between 2 and 3 m‐mole/kg axoplasm. The mobility of Mg was not changed by poisoning the axon fully.4. Mg influx and Mg efflux were roughly the same and equal to about 1 p‐mole/cm2 sec. Mg efflux was reduced by poisoning with cyanide and by replacement of external Na by choline. Removal of external K or Ca had little effect and removal of external Mg tended to increase the efflux.5. The dependence of Mg efflux on Na seems not to be secondary to changes in Ca because it persists in the absence of external Ca and in axons pre‐injected with EGTA. The form of the dependence on Na ions approximates to a simple rectangular hyperbola.6. Replacement of external Na by Li or choline increased Mg influx. Mg influx was unaffected by cyanide.7. Mg efflux was reduced to an average of 15% by poisoning with cyanide or DNP. The efflux could be recovered by injection of ATP. Inhibition persisted in axons pre‐injected with EGTA, showing that it is not secondary to a rise in Cai.8. During nervous activity there is an extra entry of Mg. For axons immersed in sea water this extra Mg entry per impulse is roughly the same as the extra Ca entry per impulse.
The influence of external caesium ions on potassium efflux in frog skeletal muscle
Authors: Beauge L. A. , Medici A. , Sjodin R. A. 
Published: December 2014

1. At a concentration of 2·5 m
M in the external solution, Cs ions reduced K efflux in muscles incubated in Na media. This effect was demonstrated in the presence or absence of 2·5 m
M‐K and in the presence or absence of 10−4
M ouabain.2. In Ringer solution in which NaCl was replaced by an osmotic equivalent of MgCl2, external Cs ions increased K efflux if the solution was K‐free and decreased K efflux if the solution contained 2·5 m
M‐K.3. External Cs ions reduced the inward rate of leakage of Na ions into muscle cells by about 25% when the medium was K‐free and contained 10−5
M ouabain.4. The effects of 2·5 m
M‐K ions and 2·5 m
M‐Cs ions on the muscle fibre membrane potential were about the same. The influence of Cs ions on K efflux cannot be explained by changes in the resting membrane potential.5. The results suggest that a large part of the K efflux from muscle cells is mediated by a K:K exchange mechanism that is inhibited by external Cs ions.6. The results also suggest that a smaller part of the K efflux is due to K:Na exchange that is also inhibited by external Cs ions.7. In the absence of either external K or Na ions for internal K to exchange with, Cs ions promote a small amount of K exchange, perhaps via both mechanisms.
Lateral inhibition in human colour mechanisms
Authors: Kelly D. H. 
Published: December 2014

1. The spatial properties of human colour mechanisms were explored by measuring contrast thresholds for sine‐wave gratings, under conditions of intense chromatic adaptation, from 0·25 to 12 cycles/degree.2. With adapting colours that tend to isolate the red‐, green‐, and blue‐sensitive spatial responses, all three results differ markedly from each other and from the neutral grating sensitivity. The green mechanism is much more sensitive than the others, the blue, much less.In all cases, the contrast sensitivity decreases at low spatial frequencies, which is typically the result of lateral inhibition. This low‐frequency inhibition effect is greatest for the unadapted case; it diminishes significantly but does not vanish when the red or green mechanism is isolated.4. These results imply that there is spatial inhibition both between and within the red and green mechanisms. Chromatic adaptation can eliminate the former but not the latter.
Maturation of glomerular blood flow distribution in the new‐born dog
Authors: Kleinman Leonard I. , Reuter John H. 
Published: December 2014

1. Glomerular blood flow distribution was studied in seventy‐eight new‐born mongrel dogs aged 1–40 days by measuring the distribution of radioactive labelled microspheres within the kidney.2. The microsphere technique was found to be a valid indicator of glomerular blood flow distribution for the new‐born dog since (a) the spheres were completely extracted by the kidney, (b) more than 95% of the spheres were trapped in glomerular capillaries, (c) the spheres were evenly distributed within any specific region of the kidney and, (d) the spheres did not interfere with renal haemodynamics.3. Plasma flow per gram tissue to inner cortical glomeruli, relative to that to outer cortical glomeruli, the IC/OC flow ratio, was high at birth, decreased over the first 2 weeks of life and remained relatively constant thereafter. Plasma flow per gram tissue to the outer cortex increased over the whole 40 day period while that to the inner cortex decreased slightly and then increased after 2 weeks.4. The IC/OC flow ratio decreased in a curvilinear fashion as blood pressure rose with maturation. Acute increases or decreases in blood pressure in any animal produced decreases or increases, respectively, in the IC/OC flow ratio.5. There was no correlation between the IC/OC flow ratio and renal extraction of p‐amino‐hippurate (E
PAH).6. There was histological evidence that glomerular differentiation persists for 2 weeks during the post‐natal period in the dog. This continuing post‐natal glomerulogenesis takes place only in the outer cortex.7. These results are consistent with the hypothesis that an important factor in renal maturation is a redistribution of blood flow within the kidney. As the animal matures a greater fraction of the total glomerular blood flow goes to outer cortical glomeruli. This is due partly to the continuing glomerular differentiation taking place in the outer cortical region and partly to the increasing arterial blood pressure occurring with maturation.
Left ventricular inotropic and peripheral vasomotor responses from independent changes in pressure in the carotid sinuses and cerebral arteries in anaesthetized dogs
Authors: Hainsworth R. , Karim F. 
Published: December 2014

1. The pressure perfusing the isolated carotid sinuses and the pressure perfusing the cerebral circulation were changed independently, and the resulting inotropic responses in the left ventricle and peripheral vasomotor responses were determined.2. Inotropic responses were assessed by measuring changes in the maximum rate of change of left ventricular pressure (dP/dt max) with heart rate and mean aortic pressure held constant. Vascular resistance changes were usually assessed by perfusing the descending thoracic aorta at constant flow and measuring changes in perfusion pressure.3. Decreases in carotid sinus pressure over the baroreceptor sensitivity range resulted in a 45% increase in dP/dt max and a 59% increase in vascular resistance.4. Unless arterial oxygen tension was abnormally low, lowering cerebral perfusion pressure to 50 mm Hg resulted in little or no inotropic and vasomotor responses. In the presence of hypoxaemia (Pa,O2 < 60 mm Hg), lowering cerebral perfusion pressure to below about 80 mm Hg resulted in marked responses.5. These experiments suggest that, unless arterial oxygen tension is abnormally low, the carotid sinus reflex and not cerebral hypotension is important in the control of the inotropic state of the heart and of vasomotor activity. With hypoxaemia, responses from cerebral hypotension may also be important.
Metabolic and ionic requirements for the intra‐axonal transport of noradrenaline in the cat hypogastric nerve
Authors: Kirpekar S. M. , Prat J. C. , Wakade A. R. 
Published: December 2014

1. Metabolic and ionic requirements for the intra‐axonal transport of noradrenaline were investigated in the cat hypogastric nerve in vitro using a histochemical fluorescence procedure.2. Specific noradrenaline fluorescence appeared at the proximal region after crushing the nerve at a distance of about 1·5 cm distal to the inferior mesenteric ganglion within 30 min, and the intensity of fluorescence increased with the perfusion time.3. Prior removal of the ganglion from the rest of the hypogastric nerve, or denervation of the ganglion, had no effect on the appearance of the specific fluorescence.4. Iodoacetic acid (5 × 10−4 M), glucose deprivation, dinitrophenol (DNP, 5 × 10−4 M) and anoxia, singly, did not affect the accumulation of noradrenaline, but combined treatment with glucose deprivation and anoxia, or glucose deprivation and dinitrophenol, very markedly interfered with noradrenaline accumulation.5. If the temperature of the perfusion fluid was reduced to 15° C, the fluorescence was not seen at the region of occlusion.6. Removal of sodium from Krebs solution markedly inhibited the axoplasmic transport of noradrenaline.7. Treatment with ouabain (10−4 M) or tetracaine (2 × 10−4 M) did not affect the appearance of specific fluorescence after occlusion.8. Our findings suggest that transport of noradrenaline storage particles within the hypogastric nerve is dependent on metabolic energy derived from either glycolysis or oxidative phosphorylation. This active process also has an absolute requirement for extracellular sodium ions.
The reflex effects of intralaryngeal carbon dioxide on the pattern of breathing
Authors: Boushey H. A. , Richardson P. S. 
Published: December 2014

1. The reflex effects on the pattern of breathing and total lung resistance of introducing 30, 10 and 5% CO2 in air into the larynx have been studied in anaesthetized and decerebrate cats breathing through a tracheostomy tube.2. Flowing 30% CO2 into the larynx caused a two‐phased response. First, respiratory frequency and tidal volume decreased, with a consequent fall in minute ventilation. After two to ten breaths, frequency remained slow, but tidal volume increased beyond the control level, so that minute ventilation was restored to control levels.3. Flowing 5 or 10% CO2 into the larynx caused slowing of breathing with small and inconsistent changes in tidal volume. Minute ventilation was significantly diminished.4. Off effects, on re‐introducing air into the larynx, after 2 and 10 min of CO2 exposure, suggested that the reflex response diminishes with increased duration of exposure to CO2.5. None of the concentrations of intralaryngeal CO2 changed total lung resistance or compliance.6. CO2 mixtures in the larynx generally caused no change in blood pressure or pulse rate of the cats.7. The reflex effects of intralaryngeal CO2 were abolished by denervating the larynx.8. Hypoxic mixtures introduced into the larynx did not change breathing.