bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparison of peripheral and rubrospinal synaptic input to slow and fast twitch motor units of triceps surae
Authors: Burke R. E. , Jankowska Elzbieta , ten Bruggencate G. 
Published: December 2014

1. Post‐synaptic potentials (PSPs) evoked by electrical stimulation of a variety of input systems have been compared in triceps surae motoneurones innervating slow and fast muscle units, the speed of contraction of which was also determined.2. Stimulation of high threshold afferents in both flexor and extensor muscle nerves, and of joint afferents, evoked polysynaptic PSPs which were predominantly hyperpolarizing in both fast and slow twitch motor units.3. Volleys in cutaneous afferents in the sural and saphenous nerves evoked polysynaptic PSPs composed of mixtures of inhibitory and excitatory components. The inhibitory components were predominant in slow twitch motor units, while in fast twitch units there was a trend towards excitatory predominance.4. Repetitive stimulation of the red nucleus caused predominantly inhibitory PSPs in slow twitch units and mixed or predominantly excitatory PSPs in fast twitch units. There was a correlation in the excitatory/inhibitory balance between PSPs of cutaneous and rubrospinal origin in those motoneurones in which both types of PSPs were studied.5. The amplitudes of group Ia disynaptic inhibitory PSPs were found to be correlated with motor unit twitch type: IPSPs in slow twitch units were larger than those in fast twitch units. Rubrospinal conditioning volleys were found to facilitate group Ia IPSPs in both fast and slow twitch motor units.6. The results suggest that there may be several basic patterns of synaptic input organization to motoneurones within a given motor unit pool. In addition to quantitative variation in synaptic distribution, there is evidence that qualitative differences in excitatory to inhibitory balance also exist in the pathways conveying input from cutaneous afferents and rubrospinal systems to triceps surae motoneurones. These qualitative differences are correlated with the motor unit twitch type.
Length changes within isolated frog muscle spindle during and after stretching
Authors: Ottoson D. , Shepherd G. M. 
Published: December 2014

1. The length changes within the frog muscle spindle during stretch have been studied by stroboscopic photomicroscopy. Attention was focused on the length changes within the central reticular zone and these changes were related to the features of the receptor potential.2. It was found that the length changes of the central reticular zone closely followed the applied stretch in time course and magnitude. The results suggest that the length changes of the polar zones are generally similar to those in the central zone.3. There was no evidence of a relative shortening of the central zone in the early phase of maintained stretch, corresponding to the decline of the receptor potential from its dynamic peak to the static level.4. Following release of stretch the central zone returned to its original resting length within a few msec. The rapid return of the spindle was in sharp contrast to the relatively slow exponential decay of the receptor potential. With strong or prolonged stretches the return became slower and resting length was not completely restored until 100–150 msec after release of stretch. No corresponding change in the decay of the receptor potential was seen.5. The results suggest that the early adaptive fall of the receptor potential is not related to differential length changes between the central zone and the polar zones. It seems more likely that the contribution of mechanical factors to the early adaptation of the frog spindle have to be sought at the ultrastructural level.6. The finding that the length changes closely follow the applied stretch suggests that the stimulus in terms of lengthening is transmitted to the endings with little distortion.7. The results suggest that the elastic elements play a dominant role for the transmission of the stimulus to the endings and for the return of the spindle to resting length after release of stretch.
An examination of nerve‐mediated, hyoscine‐resistant excitation of the guinea‐pig colon
Authors: Furness J. B. 
Published: December 2014

1. The mechanical and electrical activity of the smooth muscle of the distal colon of the guinea‐pig has been recorded in experiments designed to determine the nature of the nerve‐mediated excitation of the muscle.2. The spontaneous contractions of the colon, normally observed in vitro, were similarly antagonized by hyoscine or tetrodotoxin. However, neither drug caused complete cessation of the spontaneous activity.3. The contractile responses of the colon to repetitive stimulation of intramural nerve fibres were of two types, a primary contraction which occurred within 1 sec of the beginning of stimulation and a secondary contraction which occurred after stimulation. The primary contraction was blocked by hyoscine, usually revealing an inhibitory response to stimulation, but the secondary contraction persisted. Similar primary contractions were observed in response to stimulation of the pelvic and sometimes of the periarterial nerves.4. An initial relaxation during, and a secondary contraction after, stimulation were sometimes obtained when the periarterial nerves were stimulated. Propranolol completely blocked both the initial relaxation and the secondary contraction in response to sympathetic stimulation but did not affect either the relaxation or the secondary contraction in response to transmural stimulation.5. The direct effects of noradrenaline and adenosine triphosphate on the mechanical activity of the colon were studied. Both drugs caused a relaxation of the colon. Washout of either drug after a short exposure was followed by a period of increased activity. Especially in preparations of low tone, the initial relaxation and the secondary contraction in response to transmural stimulation could be mimicked by the application and washout of either noradrenaline or adenosine triphosphate.6. Two types of potential change were evoked in the muscle cells of the colon, either separately or in combination, when the intramural nerve fibres were stimulated: excitatory junction potentials (EJPs), which were blocked by hyoscine, and inhibitory junction potentials (IJPs). When the membrane potential recovered following an IJP, it was common to observe action potentials in muscle cells that were initially quiescent. A similar secondary firing of action potentials was initiated by hyperpolarizing the muscle cells with anodal current pulses in the presence of tetrodotoxin in sufficient concentration to block nerve‐mediated responses.7. The results reported in this paper lead to the conclusion that the muscle cells of the distal colon of the guinea‐pig are influenced by three sets of nerves: cholinergic excitatory, adrenergic inhibitory and intrinsic inhibitory fibres releasing a non‐adrenergic transmitter substance. The secondary non‐cholinergic excitation arises from a non‐specific reaction of the muscle cells to a preceding inhibition.
The influence of heart rate on the section of a substance closely resembling the 18‐monoacetate of D‐aldosterone by the hearts of cats under chloralose anaesthesia
Authors: Lockett Mary F. , Retallack R. W. 
Published: December 2014

1. A substance (HS), similar to the 18‐monoacetyl derivative of
D‐aldosterone (18 MA) in its physico‐chemical and biological properties, is shown to be secreted into the coronary circulation by cat hearts, in vivo.2. The concentrations found in coronary sinus blood from cats resting under chloralose anaesthesia ranged from 20 to 36 ng/ml. equivalent 18 MA activity.3. A positive correlation was found between heart rate and the concentration of HS in coronary sinus blood. This concentration was doubled by a rise in heart rate of 65 ± 20·2 beats/min when the tachycardia was induced by electrical drive from the right atrial appendage. An increase of only 22·5 ± 1·76 beats/min doubled the concentration of HS when the acceleration was induced by infusion of adrenaline, noradrenaline or isoprenaline or by atropinization.4. Two methods are described for bio‐assay of HS. The reference compound used was 18 MA.
The increase in the rate of heat production of frog's skeletal muscle caused by hypertonic solutions
Authors: Yamada K. 
Published: December 2014

1. The rate of heat production of resting muscle is increased by hypertonic solutions.2. The threshold osmolality required to produce the increased heat rate is less than 2 times normal; at 2·5–3 times normal the heat production rises to 20–50 mcal.g−1.min−1, which is 10–20 times the basal rate.3. In anaerobic conditions, the effect of hypertonic solutions on heat rate is only one tenth of that in aerobic conditions.4. A glycerol‐treated muscle, with damaged tubular system, still gives a normal response to hypertonic solutions, though it does not respond to raised K+ concentration.5. The metabolic response to hypertonic solutions is considerably suppressed by procaine.6. Ouabain, 10−5‐10−4
M, has no effect.7. The response remains substantial in a muscle which has been depolarized in isotonic K2SO4.8. The membrane potential is slightly reduced by hypertonic solutions, but this cannot account for the increase of the resting metabolism.9. It is suggested that the effect may be due to the release of calcium ions, which produce an increase in myosin ATPase activity.
Ouabain‐sensitive carrier‐mediated transport of glucose from the cerebral ventricles to surrounding tissues in the cat
Authors: Brøndsted H. E. 
Published: December 2014

1. Artificial cerebrospinal fluid containing isotopically labelled sugars was perfused from the lateral cerebral ventricles to an effluent catheter inserted into the cerebral aqueduct of anaesthetized cats. This system was used for a quantitative study of the absorption of the sugars during steady state.2. A saturable mechanism was involved in the absorption of [U‐14C]
D‐glucose and [14C]
D‐galactose. Absorption of [U‐14C]
D‐glucose in the dead animal was similar to that of [3H]
D‐mannitol.3. 5 × 10−5
M ouabain in the inflow reduced cerebrospinal fluid formation and the unidirectional fluxes of glucose from the ventricles into brain tissue and plasma. Ouabain did not alter the absorption of [3H]
D‐mannitol.4. Three types of unidirectional fluxes of glucose from the cerebral ventricles were separated. One was ouabain‐sensitive and followed Michaelis—Menten kinetics. The second was insensitive to ouabain and the third occurred by simple diffusion.5. At normal ventricular glucose concentrations (3·5 m
M) the three fluxes comprised (roughly): 25% (ouabain‐sensitive), 35% (ouabain‐insensitive) and 40% (simple diffusion) of total, unidirectional transport.
Changes in pattern‐evoked responses in man associated with the vertical and horizontal meridians of the visual field
Authors: Halliday A. M. , Michael W. F. 
Published: December 2014

1. Averaged responses have been recorded from an array of ten scalp electrodes over the occipital cortex in man to the reversal of a black‐and‐white checkerboard pattern, presented in different octants of the visual field.2. In all subjects a prominent wave was seen, with a peak latency of about 100 msec, which showed consistent and systematic changes with variation in the position of the stimulus in the visual field.3. With stimulation of the octants next to the vertical meridian, this component was of large amplitude, while with stimulation of the octants next to the horizontal meridian, it was small and inconspicuous.4. With upper field octants, the peak at 100 msec was surface‐negative, while with lower field octants it was reversed in polarity.5. The occipital response was largest 5 or 7·5 cm above the inion, and the amplitude recorded 3 cm lateral to the mid line was larger over the hemisphere contralateral to the half field being stimulated than ipsilaterally.6. These findings are discussed in relation to the underlying anatomy of the visual cortex, and it is concluded that these responses are likely to arise mainly from extra‐striate areas.
Caudate nucleus neurones: correlation of the effects of substantia nigra stimulation with iontophoretic dopamine
Authors: Connor John D. 
Published: December 2014

1. Extracellular recordings were made from caudate nucleus neurones in decerebrate cats using five‐barrel micropipette electrodes.2. Electrical stimulation of the substantia nigra caused spike rate depressions in 121 of 260 caudate neurones as evidenced by changes in the post‐stimulus histograms of their firing patterns. Spike rate facilitation occurred with forty‐two caudate units.3. Neurones depressed by nigral stimuli were consistently depressed by micro‐iontophoretic dopamine.4. Alpha‐methyldopamine, administered iontophoretically, antagonized the depressant responses induced by both nigral stimulation and iontophoretic dopamine.5. The data are compatible with the concept that the caudate neuronal depressant responses produced by nigral stimulation are mediated by a direct dopaminergic nigro‐neostriatal pathway. The possibility of mediation via polysynaptic pathways cannot, however, be completely excluded.
Diffusion and distribution of dimethyl sulphoxide in the isolated guinea‐pig taenia coli
Authors: Elford B. C. 
Published: December 2014

1. The diffusion of the cryoprotective non‐electrolyte dimethyl sulphoxide (DMSO) in the isolated guinea‐pig taenia coli at 37, 25 and 0° C has been studied using [35S]DMSO.2. Within 1 hr after immersion at 37° C in Krebs solution containing 20% (w/v) DMSO and trace amounts of [35S]DMSO, the non‐electrolyte was distributed uniformly throughout a volume equivalent to the total initial water content of the muscle.3. The kinetics of efflux of [35S]DMSO from muscles at constant volume were analysed on the basis of two models: one incorporated radial diffusion in extracellular fluid with simultaneous permeation into the cells, the other involved only radial diffusion in homogeneous cylinders of tissue having no internal barriers to diffusion; the former was found to give a better representation of the efflux kinetics.4. If it was assumed that the rate of diffusion of DMSO in the extracellular space of taenia coli was the same as that in the bathing medium, the values of the extracellular space and the permeability of smooth muscle to DMSO, obtained from the analysis of the efflux kinetics, were 454 ± 19 ml./kg and 2·36 ± 0·05 × 10−6 cm sec−1 at 37° C.5. The activation energy for the transfer of DMSO across the surface of the cell was estimated to be 6·0 kcal/mole at 37° C, 6·6 kcal/mole at 25° C and 11·6 kcal/mole at 0° C, indicating either that the equivalent pore radius of the cells decreased with temperature or that the cell permeability represented the sum of two fluxes, one through the aqueous pores of the cell and the other through the lipid phase of the cell membrane, each with a different energy of activation.6. A net flux of water across the surface of the cells, superimposed on the efflux of DMSO, markedly affected the rate of diffusion of the non‐electrolyte out of the whole tissue; however, it was considered that an analysis of the efflux kinetics was not possible under these conditions.7. These results provide a basis for methods which will be used to investigate the possibility of preserving tissue in unfrozen aqueous media at sub‐zero temperatures.
Structural changes in the small intestine associated with the uptake of polyvinyl pyrrolidone by the young ferret, rabbit, guinea‐pig, cat and chicken
Authors: Clarke Rufus M. , Hardy R. N. 
Published: December 2014

1. The entry of [125I]polyvinyl pyrrolidone (PVP) of mean mol. wt. 160,000 (K. 60) into the epithelial cells of the small intestine has been measured in new‐born animals of five species.2. The distribution along the intestine of cells capable of taking up [125I]PVP and the decrease and eventual cessation of uptake (closure) with increasing age have been investigated, and have been related to changes in the histological appearance of the small intestine.3. The small intestine of the ferret took up PVP readily until 33–34 days after birth. From 34 to 37 days of age PVP uptake declined sharply and disappeared completely by 40–45 days.4. In the ferret, unlike other species studied, some PVP was taken up by the duodenum. This continued for the first 4 weeks after birth. Thereafter PVP uptake gradually became confined to the terminal ileum.5. In the guinea‐pig, PVP uptake was limited to the first 48 hr after birth. During this period the site of uptake was progressively restricted to the terminal ileum.6. In the rabbit, PVP could be taken up in the distal two‐thirds of the small intestine for at least 20 days after birth. A decline in uptake occurred between 20 and 22 days after birth in most animals.7. Wide individual variations were seen in the kitten, but PVP uptake was seen in some animals up to 14 days after birth.8. Newly hatched chicks and chicks tested 48 hr after hatching did not take up PVP.9. Histological examination of the small intestine with the light microscope demonstrated that in all species PVP uptake was associated with the presence of vacuoles in the epithelial cells of the villus.10. In the young guinea‐pig, large PAS‐positive granules were seen in the macrophages of the lamina propria. These appeared to migrate through the epithelium into the intestinal lumen. The significance of this finding and its relation to macromolecular uptake remain unclear.
Neuromuscular transmission in new‐born rats
Authors: Redfern P. A. 
Published: December 2014

1. End‐plate potentials (e.p.p.s) were recorded intracellularly from the isolated phrenic/diaphragm preparation of the rat during the first few weeks of life.2. Most e.p.p.s at birth were complex and resulted from the summation of two to four units, which could be separated by their different latencies and thresholds to stimulation of the phrenic nerve.3. The e.p.p.s became simpler during the second week of the rats' life, and by 16–18 days old the e.p.p.s consisted of single units, and resembled the e.p.p.s of adult rat muscle.4. It is proposed that the units of the e.p.p. resulted from the stimulation of separate nerve axons and that all but one of the synapses on each muscle fibre were lost during the second week of life.
Electrical interaction between antidromically stimulated frog motoneurones and dorsal root afferents: enhancement by gallamine and TEA
Authors: Grinnell Alan D. 
Published: December 2014

1. Electrical interactions have been studied in the isolated frog spinal cord preparation. It is found that gallamine and tetraethylammonium chloride (TEA) markedly enhance all non‐cholinergic synaptic interactions, including the electrical interaction between motoneurones (VR‐VRP). In addition, in the presence of either of these drugs, a short‐latency interaction is seen to exist between antidromically stimulated motoneurones and dorsal root afferents (early VR‐DRP). The early VR‐DRP is rarely seen in the absence of gallamine or TEA.2. The early VR‐DRP is of the same short latency as the VR‐VRP and fulfils the same criteria for electrical interaction: it increases in amplitude with cooling from 17–10° C, it is not blocked by a wide variety of pharmacological blocking agents, and it is suppressed by both Mg2+ and Ca2+, with no antagonism of action between the two.3. The early VR‐DRP appears as a cluster of unitary events: all‐or‐none spikes conducted out the dorsal root fibres. No initial graded slow potentials are seen. Often there are two peaks in the response.4. The early VR‐DRP is facilitated by a dorsal root volley, with a time course normally intermediate between that of the orthodromic ventral root potential (DR‐VRP) and the dorsal root potential (DR‐DRP). This orthodromic facilitation apparently is achieved by increasing invasion of motoneurone dendritic trees and depolarization of dorsal root afferents toward threshold.5. If the same ventral root is stimulated twice, or adjacent roots stimulated at different intervals, the second early VR‐DRP, like the VR‐VRP, is seen to be occluded for 10–20 msec, then facilitated to supranormal amplitudes. It is concluded that motoneurone dendrites are presynaptic to both interactions.6. Evidence is presented that gallamine and TEA act by increasing the duration of activity both in axon terminals and in antidromically invaded motoneurones. Often second or multiple spikes result. The increased duration of depolarization can increase transmitter release at terminals and increase coupling at electrical junctions.7. Possible morphological correlates for the two electrical interactions are discussed. It is speculated that the motoneurone interaction arises at numerous areas of close apposition between dendrites in dendritic ‘thickets’, and that the early VR‐DRP is mediated by fewer, lower‐resistance, electrical junctions between dendrites and afferent nerve terminals.
The visibility of transient changes of luminance
Authors: Rashbass C. 
Published: December 2014

1. The threshold intensities of various transient changes from a base line luminance in the mid‐photopic range have been measured.2. Rectangular changes in luminance show no difference between increments and decrements, a threshold intensity decreasing inversely with durations up to 16 msec, a lesser reduction in threshold up to 64 msec and for longer durations a slight increase in threshold.3. Two brief flashes separated by an interval show incomplete summation at 10 msec, almost no summation at 65 msec and a second reduction in threshold at 100 msec.4. Two brief flashes in opposite directions negate each other at very small intervals but complement each other at longer intervals, maximally at 65 msec.5. A model of the detector system is proposed that passes the stimulus wave form through a band‐pass filter and takes a running average of the variance of the filter output. Threshold is reached if this average attains a certain level.6. The model satisfactorily accounts for the observations that any two wave forms occurring together and not exceeding a total of 100 msec in duration will interact so that the relationship between them at the combined threshold will be an ellipse; and that this ellipse will have no obliquity if one wave form is the differential of the other.7. Measurements of the thresholds of two brief flashes separated by various intervals define the attenuation characteristics of the band‐pass filter invoked to explain the thresholds of repetitive stimuli.8. The model reconciles the apparent disparity between the thresholds of single flashes of varying duration and pairs of flashes of varying interval.9. The statistical efficiency of such a system is discussed.
Glucose‐induced electrical activity in pancreatic islet cells
Authors: Dean P. M. , Matthews E. K. 
Published: December 2014

1. Intracellular recording of the transmembrane potential in mouse pancreatic cells revealed a membrane potential of −20·1 ± 0·8 mV for islet cells and −41·2 ± 1·4 mV for acinar cells.2. The membrane potential of islet cells was glucose dependent and in the absence of glucose the cells hyperpolarized to −32·7 mV; with glucose 27·7 m
M they depolarized to −16·1 mV.3. Above a threshold concentration of glucose (4 m
M) small action potentials of amplitude 1‐4 mV were induced in islet cells. The percentage of cells impaled exhibiting action potentials reached a maximum of 80% at 27·7 m
M glucose.4. Mannose 16·6 m
M was similar to glucose in its ability to induce action potential discharge in islet cells.5. 2,4‐Dinitrophenol (0·25 m
M) hyperpolarized islet cells and blocked electrical activity induced by glucose 11·1 m
M.6. Adrenaline (1 μ
M) completely blocked glucose‐induced electrical activity but without altering the membrane potential.7. The origin and functional significance of glucose‐induced electrical activity in islet cells is discussed in relation to insulin secretion.