bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional properties of monkey motor cortex neurones receiving afferent input from the hand and fingers
Authors: Lemon R. N. 
Published: December 2014

1. Records have been made from area 4 of the cerebral cortex in five conscious monkeys. The properties of 216 neurones responsive to natural stimulation of the hand and fingers have been investigated.2. 46% of these neurones responded only to cutaneous stimulation (especially light brushing across the glabrous skin) and a further 38% responded only to movement of the digits. 4% responded to brief prods of the hand. 12% of the sample responded to more than one stimulus modality.3. Many hand‐input neurones, including pyramidal tract neurones, responded at short‐latency (8‐15 msec) to light mechanical stimulation of the hand and to weak electrical stimulation of the median nerve.4. Responsive neurones were found at all depths of the cortical grey matter. Responses of shortest latency were encountered in neurones probably located in layers IV and V.5. The behaviour of eighty hand‐input neurones was analysed during a simple, stereotyped task which involved pulling a lever and collecting a food reward from a small well. For comparison, the activity of 117 neurones with inputs from the wrist, elbow or shoulder was also analysed.6. Nearly all hand‐input neurones modulated their activity either before (48/80) or during (29/80) the retrieval of the reward which required precision grip between index finger and thumb. Many were silent during proximal arm movements and some displayed activity patterns independent of these movements.7. By contrast, the activity of many neurones with proximal arm (elbow, shoulder) inputs was unrelated to food retrieval and manipulation, but well related to arm movements.8. Forty‐three of the eighty neurones had cutaneous input from the hand. Twenty‐seven were active before hand contact. Thirty‐five modulated their discharge when contact was made (twenty‐one excitation, fourteen inhibition).9. Most hand‐input neurones were more active during fractionated movements of the hand or fingers than during power or ball grips requiring simultaneous flexion of all digits. Neurones with glabrous inputs often showed intense activity during small, precise finger movements and during active tactile exploration without the aid of vision.10. Analysis of the discharge frequency of twenty‐five hand‐input neurones revealed that some (mainly non‐pyramidal tract neurones) had a similar mean frequency and range of modulation during both active movement and passive stimulation. Others (mainly pyramidal tract neurones) had a greater frequency range and higher mean frequency during active than during passive movements.
Epithelial solute permeability, ion transport and tight junction morphology in the developing lung of the fetal lamb
Authors: Olver R. E. , Schneeberger E. E. , Walters D. V. 
Published: December 2014

1. Experiments were performed on exteriorized fetal lambs of between 69 days' gestation and term (147 days) in order to observe changes in lung volume and lung liquid secretion rate, and to delineate any alterations in solute permeability, ion transport and tight junction morphology in the maturing lung epithelium. Whilst it was technically possible to measure solute permeability as early as 69 days it was not feasible to apply the Ussing flux ratio technique before 84 days.2. Fetal lung liquid volume and secretion rate, when normalized for body weight, increase linearly with gestation, whereas tracheal volume expressed in the same manner remains constant.3. When expressed in terms of pore theory, epithelial permeability to small polar non‐electrolytes does not change between 69 days and term (equivalent pore radius 0.66 nm and 0.64 nm respectively).4. In the immature fetus of 69‐76 days, mean epithelial tight junction strand number is 8.3, whereas by the end of gestation it has fallen to 4.6.5. The transfer constants (min−1) for sodium and chloride movement in the direction lung liquid to plasma are, respectively, some 6 and 4 times greater at 84‐87 days than at term.6. As in the mature fetus, the lung epithelium at 84‐87 days actively transports chloride from plasma to lung lumen, albeit with a slightly reduced transport e.m.f. Sodium movement does not, at any gestational age, differ from the predictions for passive transfer.7. In lung liquid the concentrations of chloride and potassium increase and that of bicarbonate decreases during gestation, whilst that of sodium does not change. The rises in lung liquid chloride and potassium concentrations follow those in plasma, maintaining plasma/lung liquid ratios of 0.7 and 0.95 respectively. However, plasma bicarbonate remains constant and the plasma/lung liquid ratio for bicarbonate rises from 3 at 69‐76 days to 20 near term as the lung liquid bicarbonate falls from 9.8 to under 2 m‐mole kg−1 H2O.8. Whereas lung liquid protein concentration remains constant and low at about 0.35 g l.−1, plasma protein concentration rises from 23 g l.−1 at 69‐76 days to 43 g l.−1 near term. During the same period arterial blood pressure doubles.
Modulatory influences of moving textured backgrounds on responsiveness of simple cells in feline striate cortex
Authors: Hammond P. , MacKay D. M. 
Published: December 2014

1. The modulatory influences of synchronously moving textured backgrounds on responsiveness to optimally oriented moving bar stimuli were investigated in 107 simple cells, with incidental observations on four complex cells, recorded in the lightly anaesthetized feline striate cortex.2. Background motion depressed bar responsiveness in 74% of simple cells, facilitated bar responsiveness in 4%, and was without influence in 22%. These results confirm our earlier observations (Hammond & MacKay, 1977).3. Moving chequerboard patterns typically elicited stronger effects than moving visual noise.4. Occluding a moving background by a mask of stationary texture of variable width and length indicated that the zone of background influence extended well beyond the excitatory receptive field along its axis, but not transverse to it. This was confirmed by a converse experiment using a window of moving texture in an otherwise stationary background.5. The influence of background motion varied markedly with location relative to the cell's receptive field. A small stationary rectangular window of moving texture at different locations along the receptive field axis typically suppressed bar response when over the receptive field, but facilitated it at either end. Conversely, with the background moving and the masking texture stationary, suppression was minimal when the masking patch was centred over the receptive field.6. Systematically varying the phase relationship between bar and background motion showed the interaction in simple cells to be greatest for in‐phase motion and least for motion in antiphase. The opposite is true for complex cells.7. All the above effects showed non‐linearities and could be enhanced by making texture velocity greater than bar velocity or by selecting the polarity of contrast and length of a bar stimulus of optimal orientation and width so as to elicit relatively weak (submaximal) criterion responses.8. Since textured backgrounds themselves evoke no response from simple cells, and since all specific afferents are known to be excitatory, it seems likely that textural influences upon simple cells are mediated only through complex cells.
Spatial spread of activation and background desensitization in toad rod outer segments
Authors: Lamb T. D. , McNaughton P. A. , Yau K.-W. 
Published: December 2014

1. The spread of activation and background desensitization in rods was studied by recording membrane current from single outer segments in pieces of isolated toad retina.2. Flash sensitivity changed slightly along the outer segment, falling by about 30% from base to tip.3. When only the distal half of an outer segment was in the recording pipette, illumination of the unrecorded part elicited little or no photocurrent at the recorded part, indicating that a photoisomerization does not cause activation of the entire outer segment.4. With diffuse illumination of an outer segment fully drawn into the pipette, the intensity—response relations at fixed times were invariant in form for most of the rising phase of the flash response and were considerably steeper than the Michaelis relation. The observed relation was consistent with a model in which a photoisomerization blocks all channels over a short region of the outer segment.5. With illumination restricted to a narrow transverse slit, the intensity—response relations at fixed times were much less steep, as would be expected for a very limited longitudinal spread of activation. An upper limit for the effective longitudinal diffusion coefficient of the internal transmitter was estimated to be about 3 × 10−7 cm2 sec−1. This corresponds to a space constant for longitudinal spread of transmitter of about 3 μm at the time of the dim response peak.6. The time course of flash responses elicited with light positioned either on the edge or on the centre of the outer segment was very similar.7. Desensitization resulting from steady illumination by a transverse slit was also localized longitudinally. A linear desensitization parameter T, defined in Results, decayed approximately exponentially along the outer segment, on either side of the site of photoisomerization, with a space constant of about 6 μm.8. Transverse spread of desensitization was more effective than longitudinal spread.9. After turning off a dim diffuse background light, the decay of T was roughly exponential with a time constant of several seconds. From this, and the steady state space constant of 6 μm, it is estimated that the effective longitudinal diffusion coefficient for a ‘desensitizing substance’ would also be about 10−7 cm2 sec−1.10. The restricted longitudinal spread of activation and desensitization may be explained by the barrier to diffusion presented by the stacked membranous disks in the outer segment. This baffling reduces the effective longitudinal diffusion coefficient to about 1/50 that of ordinary aqueous diffusion, but it does not significantly affect transverse spread.
Mediators of slow synaptic potentials in the myenteric plexus of the guinea‐pig ileum
Authors: Johnson S. M. , Katayama Y. , Morita K. , North R. A. 
Published: December 2014

1. Intracellular recordings were made from neurones in the myenteric plexus of the ileum isolated from adult guinea‐pigs.2. Three synaptic potentials were evoked in different myenteric neurones by focal stimulation of the ganglion surface at a distance of up to 100 μm from the cell body from which the recording was made. These were the fast cholinergic excitatory post‐synaptic potential (e.p.s.p.), the slow e.p.s.p. and the slow inhibitory post‐synaptic potential (i.p.s.p.).3. 5‐hydroxytryptamine and substance P were applied to the neurones by superfusion (10 n
m‐1 μ
m) or by electrophoresis within 5 μm of the neurone cell body. 5‐HT depolarized, hyperpolarized or had no effect on approximately equal numbers of neurones, whereas substance P depolarized 90% of neurones.4. Many neurones with a depolarizing slow e.p.s.p. were hyperpolarized by superfusion or electrophoretic application of 5‐HT.5. Superfusion with 5‐HT reversibly depressed the fast e.p.s.p., slow e.p.s.p. and slow i.p.s.p. Superfusion with substance P depressed the slow e.p.s.p.6. Methysergide (10‐30 μ
m) reduced the amplitude of the fast e.p.s.p., the slow e.p.s.p. and the slow i.p.s.p.7. Chymotrypsin (200 μg/ml.) reversibly reduced the amplitude of the slow e.p.s.p., but had no effect on membrane potential, the action potential or the fast e.p.s.p. Chymotrypsin reduced or abolished the depolarization caused by electrophoretic application of substance P, but had no effect on the depolarization or hyperpolarization caused by 5HT.8. The results provide evidence that 5‐HT is not the transmitter which mediates the slow e.p.s.p. in myenteric neurones. The slow e.p.s.p. may be caused by substance P or another similar peptide.
Two groups of spinal interneurones that respond to stimulation of the abdominal viscera of the cat
Authors: McMahon S. B. , Morrison J. F. B. 
Published: December 2014

1. Recordings have been made from sixty‐three spinal interneurones that received inputs from the abdominal viscera. These were divided into two groups: group A were sacral interneurones without either significant ascending projections or afferent input from the lumbar splanchnic nerves and group B were neurones with short ascending axons and afferent inputs from the lumbar splanchnic nerves, and often also from the pelvic and pudendal nerves.2. Somato‐visceral convergence was common in both groups, and the somatic receptive fields of group A interneurones were in muscle and joints and less commonly skin innervated by sacral segments, whereas those of group B were innervated by lumbar and sacral segments.3. Within both groups of neurones there was a proportion that showed no response to distension or contractions of the viscera, (despite the fact that they responded to visceral nerve stimulation), and those which did respond showed graded changes in discharge rate as intravesical pressure was raised. Some cells received inputs from only one viscus: the receptive fields of these cells are described as simple and the effect of raising the pressure in that viscus was either to excite or to inhibit the central neurone. Other cells received convergent inputs from two viscera: their receptive fields are described as compound and the effect of raising intraluminal pressures in the viscera allowed a further subdivision of these cells into two types. Type I cells were either excited or inhibited by distension or contractions of either viscus. Type II cells were excited by natural stimulation of one of the innervated viscera but inhibited by similar changes in the other. The static pressure thresholds of these cells were 9±5 mmHg intravesical pressure, and 24±11 mmHg intracolonic pressure (means±
s.d.).4. It is proposed that within the population of neurones described there are cells (group A interneurones) that either mediate the vesico‐ and colono‐sphincteric reflexes or the colono‐vesical interactions that can be seen in the micturition reflex pathway.5. It is proposed that the group B interneurones with short ascending projections mediate the vesico‐ and colono‐sympathetic reflexes because their patterns of convergence, position in the spinal cord, latencies, and static pressure thresholds are consistent with those reflexes.
Paracellular non‐electrolyte permeation during fluid transport across rabbit gall‐bladder epithelium
Authors: Steward Martin C. 
Published: December 2014

1. Mucosa‐to‐serosa fluxes of seven polar non‐electrolytes were determined during isotonic fluid transport across the unilateral rabbit gall‐bladder preparation in an attempt to estimate the contribution of the paracellular pathway to the total transepithelial water flow.2. 3H‐ and 14C‐labelled non‐electrolyte tracers appeared in the transported fluid at fractions (fn) of their mucosal concentration which were inversely related to molecular size: ethanediol, 0·80; thiourea, 0·55; glycerol, 0·16; erythritol, 0·11; mannitol, 0·05; sucrose, 0·05; inulin, 0·02. The mean volume flow rate was 78 μl. cm−2 hr−1.3. While the fluxes of the larger molecules were probably due to diffusion through a small but unrestricted paracellular ‘shunt’ permeability, the high fn values obtained for the smaller molecules indicate the existence of a substantial paracellular permeability restricted to molecules smaller than erythritol.4. Upper limits to the transcellular ethanediol and thiourea permeabilities, estimated from the time constants of tracer efflux from preloaded epithelial cells, were too low to account for more than a very small fraction of the transepithelial fluxes observed in the unilateral preparation.5. Comparison of the fn values with the predictions of a hydrodynamic model of paracellular permeation suggests that in order to account for the large fluxes of ethanediol and thiourea, considerably more than one half of the transepithelial water flow must follow the paracellular pathway.6. Following a reduction of the mucosal osmolality to 110 m‐osmole kg−1, the apparent non‐electrolyte permeability of the epithelium increased steadily over a period of 4 hr. This seems to reflect an increase in the shunt permeability rather than a change in the selectivity of the restricted permeability.7. It is concluded that during isotonic fluid transport the bulk of the transepithelial water flow crossing the epithelium passes through paracellular channels of approximately 3 Å radius which are probably located in the intercellular junction.
Post‐tetanic depolarization in sympathetic neurones of the guinea‐pig
Authors: Dun N. J. , Minota S. 
Published: December 2014

1. Repetitive intracellular stimulation at a frequency of 5‐30 Hz for 1‐10 s evoked in neurones of the isolated inferior mesenteric and superior cervical ganglia of the guinea‐pig three types of post‐spike membrane potential changes: (i) hyperpolarization, (ii) hyperpolarization followed by a slow depolarization, and (iii) a second hyperpolarization following the initial two responses.2. The initial post‐spike hyperpolarization had a mean duration of 2·0 s and was often associated with a fall in membrane resistance; it could be elicited in every sympathetic neurone studied. This response was termed the post‐tetanic hyperpolarization (PTH).3. The slow depolarization which could be induced only in a portion of neurones had a mean amplitude and duration of 2·2 mV and 27·5 s, respectively; it was termed the post‐tetanic depolarization (PTD).4. PTD was associated with a fall in membrane resistance, augmented by membrane hyperpolarization, and reduced by depolarization; its mean extrapolated equilibrium potential was ‐38 mV.5. PTD was not blocked by nicotinic and muscarinic antagonists, or α‐and β‐adrenergic receptor antagonists, whereas it was suppressed by adrenaline, noradrenaline, Co2+ and a low Ca2+ solution.6. The amplitude of the single spike after‐hyperpolarization in normal Krebs solution as well as in high K+ solution was increased during PTD; furthermore, conditioning hyperpolarization to the level of EK increased the amplitude of PTD in normal Krebs as well as in high K+ solution.7. PTD with similar amplitude, time course and membrane characteristics could be evoked in a portion of neurones of the rabbit superior cervical ganglia; however, PTD was not detected in neurones of the rat superior cervical ganglia.8. Decentralization of the guinea‐pig and rabbit superior cervical ganglia for 14 d did not alter the number of neurones in which PTD could be elicited, its amplitude, or its time course.9. Our results suggest that a chemical substance(s) is responsible for the generation of PTD; it may be released from the soma and/or dendrites and acts in an auto‐receptive manner on the cells in question. The nature and origin of the second hyperpolarization remain to be clarified.
A transcortical loop demonstrated by stimulation of low‐threshold muscle afferents in the awake monkey
Authors: Chofflon M. , Lachat J.-M. , Rüegg D. G. 
Published: December 2014

1. The hypothesis that a transcortical loop can be activated by electrical stimulation of low‐threshold muscle afferents was tested. The effect of these afferents on the excitability of motoneurones was measured with the monosynaptic spinal reflex (H‐reflex).2. Four monkeys were trained to maintain a constant tonic activity in the soleus muscle so that the amplitude of evoked H‐reflexes was constant. The intensity of conditioning stimuli was just subthreshold for direct or reflex electromyographic responses. The intensity of the test stimuli was adjusted to evoke an H‐reflex of maximal amplitude. The amplitude of the H‐reflex was recorded for different intervals between conditioning and test stimuli (10‐1000 msec).3. The excitability curve obtained showed three components: (1) an early excitatory process, F1, at intervals of 10‐20 msec, (2) a late excitatory process, F2, at intervals of 40‐80 msec and (3) a short latency depression of about 400 msec duration, on which F1 and F2 were superimposed.4. F2 was selectively abolished during cooling of the contralateral motor cortex, after an irreversible lesion of the motor cortex, and after pyramidotomy; however, F1 and the inhibition remained unchanged.5. The conduction time from the tibial nerve to the somatosensory cortex (SI), the cortical delay between SI and motor cortex, and the conduction time from motor cortex to the soleus muscle were measured in an anaesthetized animal. The sum of these values as an estimate of the transcortical loop time was 5 msec shorter than the latency of F2.6. It is concluded that a transcortical loop can be activated by electrical stimulation of low‐threshold muscle afferents and, by analogy, also by mechanical perturbations applied during a motor task.
Effects of adenosine and its analogues on the perfused hind limb artery and vein of anaesthetized dogs
Authors: Cotterrell D. , Karim F. 
Published: December 2014

1. The effects of infusion of adenosine and its analogues on arterial and venous resistance have been studied in the vascularly and sympathetically isolated hind limb of chloralose‐anaesthetized dogs. Resistance changes have been assessed by monitoring changes in perfusion pressures at constant flow through the femoral artery and metatarsal vein.2. With sympathetic stimulation (10 V, 2 msec, 0·5‐2 Hz applied to the cut peripheral end of the lumbar sympathetic trunk), continuous infusion of adenosine, to produce a concentration of approximately 2 × 10−5
m, resulted in a near maximal sustained decrease in arterial perfusion pressure of 35·3±3·6%, and a decrease of about half this in venous perfusion pressure.3. Bolus injections of adenosine into the artery, to produce a concentration of about 7 × 10−5
m, caused a transient decrease in resistance similar to that observed with continuous infusion. However, the venous response was smaller than that induced by continuous infusion.4. Withdrawal of sympathetic stimulation to the limb had little effect on adenosine‐induced vasodilatation in the artery, but abolished the small response of the vein.5. Less than 5% vasodilatation was produced in the artery and vein by 2‐deoxyadenosine, inosine, guanosine, xanthosine, cytidine or uridine when infused in amounts up to ten times, or by sodium phosphate (pH 7·4) in amounts one hundred times the maximal amounts of adenosine given.6. These results suggest that adenosine caused vasodilatation, at least in arterioles, largely by acting directly on vascular muscle rather than via presynaptic inhibition of noradrenaline release.