bluuebunny/crossref_metadata_2025 huggingface dataset:
The size of rod signals
Authors: Alpern M. , Rushton W. A. H. , Torii S.
Published: December 2014

1. This investigation is based upon Alpern's (1965) contrast flash observations. The threshold for the test flash λ (Fig. 2a) is raised if a second flash ϕ falls on the annular surround. Moreover, if λ excites rods at threshold, it is only the rods in the surround that contribute to the threshold rise.

2. The possibility that the rise in λ threshold might be due to light physically scattered from surround to centre we exclude by several different experiments. We conclude (Fig. 1b) that the ϕ flash sets up a nerve signal N which is conducted to some place C where it inhibits the signal from the centre.

3. If the luminous surround, instead of being a full circle (Fig. 2a) consists only of the sectors shown black in Fig. 2b, that occupy 1/m of the surround area, it is found (in the physiological range) that the light/area on those sectors must be m times as great to produce the same threshold rise at centre, i.e. the total surround illumination must remain the same.

4. This result would obviously follow if N, the inhibitory nerve signal, were proportional to the total surround illumination. We have established the converse; the signal must be proportional to the quantum catch.

5. Light can be increased indefinitely, nerve signals cannot. When ϕ increases sufficiently, N saturates in the same way that S‐potentials and receptor potentials saturate, namely according to N = ϕ/(ϕ + σ) where σ, the semi‐saturation constant is about 200 td sec, or 800 quanta absorbed per rod per flash.

6. Thus the nerve signal N is proportional to the quantum catch over 4 log units in the physiological range, namely from 1 quantum per 100 rods to 100 quanta per rod per flash. Above this for another 2 log units N continues to increase, but now more slowly, after the manner of S‐potentials and receptor potentials.
Irreversible impairment of thermoregulation induced by capsaicin and similar pungent substances in rats and guinea‐pigs
Authors: Jancsó-Gábor Aurelia , Szolcsányi J. , Jancsó N.
Published: December 2014

1. In rats and guinea‐pigs a subcutaneous or intraperitoneal injection of capsaicin, the substance responsible for the pungency of red pepper, produces profound hypothermia associated with skin vasodilatation.

2. After large doses of capsaicin rats and guinea‐pigs become insensitive to the hypothermic action of capsaicin. This densensitization is apparently irreversible since it is present months after the capsaicin treatment.

3. Capsaicin‐desensitized animals are no longer able to protect themselves against overheating but respond with pronounced hyperthermia to high ambient temperatures (32–40° C). Temperature regulation against cold exposure, however, is not impaired.

4. They also respond with an enhanced hyperthermia to painful stimuli such as repeated pinching of the tail or repeated introduction of the thermometer probe into the rectum.

5. The enhanced hyperthermias are not due to increased heat production but to impairment of the heat dissipating mechanisms, which in rats and guinea‐pigs acts mainly through evaporation of saliva, and skin vasodilatation.

6. Acylamides with pungent action related to capsaicin such as piperine, caprinoyl‐p‐aminophenol and propionyl vanillylamide also cause hypothermia followed by desensitization and their efficacy is dependent on their pungency. The non‐pungent nonenoyl benzylamide produces neither hypothermia nor desensitization.

7. Capsaicin and its related pungent acylamides appear first to stimulate and then to desensitize the hypothalamic warmth detectors. By stimulating them the acylamides evoke reflexly the hypothermic response, whereas after desensitization the protective thermoregulatory reflexes for heat dissipation are no longer activated in response to high ambient temperature and to painful stimuli.
Short‐circuit current and ionic fluxes in the isolated colonic mucosa of Bufo arenarum
Authors: Lew V. L.
Published: December 2014

1. The unidirectional fluxes of 22Na, 36Cl and [14C]bicarbonate ions were measured in paired portions of the isolated and short‐circuited colonic mucosa of Bufo arenarum, separated from its muscular layer. Pharmacological effects as well as effects of changes in the composition of the nutrient solutions on the electrical parameters of membrane activity (potential difference, short‐circuit current and total membrane resistance) are described.

2. The net fluxes of both Cl and bicarbonate ions were not significantly different from zero in the absence of electrochemical gradients across the membrane.

3. The net Na flux from mucosa to serosa represented a variable proportion of the short‐circuit current ranging from 62 to 100%.

4. The proportion of membranes with high discrepancies between net Na flux and short‐circuit current decreased with the duration of captivity of the toads.

5. When Na was entirely replaced by choline in the mucosal bathing solution, the short‐circuit current dropped by a variable amount within the range of 64 to 98% of its control values in different membranes. This effect was completely reversible. Similar changes in the serosal solution had no effect.

6. The short‐circuit current and potential difference were very sensitive to the serosal concentration of bicarbonate ions. In different membranes, 60–100% of the short‐circuit current was reversibly abolished by bathing the serosal surface with a bicarbonate‐free solution. The mucosal bicarbonate level had no effect on either the potential difference or the short‐circuit current. 5 m
M bicarbonate in the serosal solution restored at least 50% of the short‐circuit control value and full recovery was attained by concentrations near 30 m
M bicarbonate.

7. Anoxia brought the potential difference and short‐circuit current reversibly down to zero in about 50 min.

8. Ouabain reduced the short‐circuit current up to 80% in about 40 min when present in the serosal solution at a concentration of 10−4
M. At this or lower concentrations the ouabain effect was reversible. Above this level ouabain produced 100% inhibition in 3‐4 hr, but this was no longer reversible. Ouabain had no effect on the short‐circuit current either when applied to the mucosal surface or in the absence of Na from the mucosal solution.

9. Diamox produced a variable inhibition of the short‐circuit current of up to 30% only at concentrations above 10 m
M.

10. Possible mechanisms are discussed for the appearance of the non‐Na component of the short‐circuit current. A theory concerning its nature is proposed.
Some effects of nerve stimulation and hemicholinium on quantal transmitter release at the mammalian neuromuscular junction
Authors: Jones S. F. , Kwanbunbumpen Suthiwan
Published: December 2014

1. Rat phrenic nerve—diaphragm preparations have been used to assess some effects of prolonged nerve stimulation on transmitter release.

2. The amplitude of the end‐plate potentials evoked by prolonged repetitive nerve stimulation fell gradually during stimulation. Most of this fall was due to a reduction in the number of transmitter quanta released by each nerve impulse; however there was also a small reduction in the muscle cell depolarization produced by each quantum of transmitter.

3. Repetitive nerve stimulation also produced a small reduction in the amplitude of the miniature end‐plate potentials. Recovery of amplitude occurred within about 7–8 min of ceasing stimulation.

4. A much greater reduction in miniature end‐plate potential amplitude accompanied prolonged nerve stimulation if hemicholinium was present in the bathing solution.

5. Estimates of the ‘readily available transmitter’ (Elmqvist & Quastel, 1965b) were made at intervals following prolonged nerve stimulation. Readily available transmitter was reduced, and recovered over approximately 15 min.

6. The relationship of these changes to the changes in nerve terminal synaptic vesicle numbers and volumes induced by similar prolonged nerve stimulation (Jones & Kwanbunbumpen, 1970) is discussed.
Synaptic connexions of alpha extensor motoneurones with ipsilateral and contralateral cutaneous nerves
Authors: Rosenberg M. E.
Published: December 2014

1. Synaptic responses of alpha extensor motoneurones to stimulation of cutaneous nerves of the hind limb were recorded from the lumbosacral region in decerebrate and decerebrate‐spinal unanaesthetized cats. Responses to ipsi‐ and contralateral stimulation are compared.

2. Usually a single volley in an ipsilateral cutaneous nerve led to an inhibitory post‐synaptic potential while one in a contralateral cutaneous nerve led to an excitatory post‐synaptic potential or to discharge of the cell, thus demonstrating the classical reciprocal innervation pattern. In some cells either ipsilateral or crossed spinal action was of opposite sign to normal.

3. Tests using graded stimulation showed the range of myelinated afferents associated with crossed spinal actions to be narrower than that for ipsilateral actions; for the sural nerve the ranges are 1‐6 μ and 1‐9 μ respectively. A substantial proportion of the coarser myelinated afferents do not make connexion with alpha motoneurones on either side of the cord; in the sural nerve this proportion includes the range 10–17 μ.

4. Central transmission times for ipsilateral and crossed‐spinal actions were estimated after making systematic allowance for conduction time to the cord in the associated cutaneous afferents. Mean values for inhibitory pathways from ipsilateral cutaneous nerves were about 2 msec, while those for crossed spinal facilitatory pathways were notably greater, 3‐5 msec.

5. Crossed spinal actions were more profoundly depressed by anaesthesia than were corresponding ipsilateral actions.

6. Interpretation of the results was aided by a separate study of the input to the spinal cord; stimulus strength is related to the diameters of the cutaneous fibres excited and to peripheral conduction time in those fibres.
The attenuation of rod signals by bleachings
Authors: Alpern M. , Rushton W. A. H. , Torii S.
Published: December 2014

1. Contrast flash technique allows the rod threshold to be measured even when it lies far above the cone threshold. In this way the rod dark adaptation curve after rhodopsin bleaching can be measured over 6 log units.

2. By retinal densitometry the regeneration of rhodopsin can be measured in the same subject. It is found that the log threshold is raised 1·2 units for each 10% of rhodopsin in the bleached state.

3. We have tried to discover whether bleaching raises the threshold by desensitizing the rods, or (like backgrounds) by attenuating their signals. Neither suggestion satisfies all conditions.

4. All are satisfied by [Formula: see text], where N is the size of rod signal, constant for threshold; θ, θD are steady backgrounds of light and receptor noise; ϕ is the threshold flash with σ a constant of about 2·5 log td sec; B the fraction of pigment in the bleached state.
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.
Drinking induced by injection of angiotensin into the brain of the rat
Authors: Epstein A. N. , Fitzsimons J. T. , Rolls Barbara J.
Published: December 2014

1. When applied directly to the brain, angiotensin II amide, as either the valine5 octapeptide, causes rats in normal fluid balance to drink water.

2. The drinking response to angiotensin injections is copious, rapid, repeatable within the same test session, and stable over months of testing in the same animal.

3. The response is motivationally potent and specific. After injection the animals move directly to the source of water and drink. There is typically no preliminary hyperactivity or subsequent depression. The animals do not eat, gnaw or exhibit other behaviours that are not normally seen during spontaneous drinking. The injections rouse sleeping animals to drink and interrupt eating in animals deprived of food for two days.

4. The region of the brain that is most sensitive to angiotensin includes the anterior hypothalamus, the preoptic region, and the septum including the nucleus accumbens.

5. Intracranial renin elicited drinking. Bradykinin and vasopressin did not, nor did adrenaline, noradrenaline or aldosterone. In the most sensitive region, sites positive for angiotensin also yielded drinking to carbachol.

6. Responses were obtained with 5 ng (ca. 5 p‐mole) and occurred reliably with 50 ng angiotensin or more. The dose—response curve for amount drunk rose from 5 to 100 ng and levelled off thereafter. Angiotensin is therefore the most potent dipsogen known and is effective at doses that are reasonably within the concentration range for circulating endogenous angiotensin.

7. Injections into the sensitive region of doses of angiotensin that were effective for drinking did not produce peripheral haemodynamic changes in lightly anaesthetized rats.

8. This work strengthens the suggestion that angiotensin is a natural hormone of drinking behaviour that participates in extracellular thirst by its release from the kidney and subsequent direct action on a specific chemoreceptive region in the anterior diencephalon and limbic lobe.
Spontaneous activity of neurones of nucleus reticularis thalami in freely moving cats
Authors: Mukhametov L. M. , Rizzolatti G. , Tradardi V.
Published: December 2014

1. Fifty‐four neurones of the caudal part of the nucleus reticularis thalami (nuc. ret.) were recorded during different phases of sleep and wakefulness in unanaesthetized freely moving cats.

2. During wakefulness the activity of the neurones was characterized by a continuous, well‐spaced discharge. The mean firing rate was 35·58 ± 15·06 spikes/sec (average ±
S.D.).

3. During sleep with synchronized e.e.g. (S‐sleep) the neurones fired in high frequency bursts with long pauses in between. Each burst was formed of 10–15 spikes. Often the bursts were followed by prolonged discharges formed of spikes well spaced one from the other. Bursts followed by prolonged activity were more commonly observed at the beginning of S‐sleep and during the S‐sleep periods preceding sleep with desynchronized e.e.g., whereas bursts immediately followed by silence were more frequent in the S‐sleep periods with e.e.g. delta waves. The long periods of silence between the bursts usually lasted over 200 msec and values greater than 1 sec were frequently found. The mean firing rate of neurones during S‐sleep was 19·22 ± 10·50 spikes/sec.

4. During sleep with desynchronized e.e.g. (D‐sleep) the activity of the neurones was, as during wakefulness, characterized by a continuous, well spaced, unclustered discharge. The mean firing rate was 40·00 ± 18·74 spikes/sec. During the rapid eye movements of this phase most units increased the frequency of their discharge, which, nevertheless, maintained the unclustered feature proper to the desynchronized phase of sleep.

5. Interspike interval distribution was similar during wakefulness and sleep with desynchronized e.e.g., whereas that for sleep with synchronized e.e.g. was markedly different from those for both the other stages.

6. The implications of the striking similarity between the activity of reticularis neurones during wakefulness and sleep with desynchronized e.e.g. are discussed.
Time course of the sodium permeability change during a single membrane action potential
Authors: Atwater Illani , Bezanilla Francisco , Rojas Eduardo
Published: December 2014

1. A method for measuring the time course of ionic fluxes during a non‐propagated membrane action potential is described; the technique combines intracellular perfusion of the squid giant axon with radioactive tracer methods and with a method for controlling the membrane potential during small time intervals.

2. The method is used to determine the temporal course of the sodium extra influx during an action potential.

3. The results agree with the time course of the permeability change to sodium ions calculated with the Hodgkin & Huxley equations.

4. An average extra sodium influx of 7·13 p‐mole/cm2 per action potential was determined at 12° C and of 5·23 p‐mole/cm2 per action potential at 15° C.
The activity characteristics of the preganglionic pupilloconstrictor neurones
Authors: Sillito A. M. , Zbrożyna A. W.
Published: December 2014

1. Recordings have been made of pupilloconstrictor unit activity within the small‐celled component of the oculomotor nucleus of the cat. The identity of these neurones was determined by testing unit responses to a sequence of stimuli which produced dilation and constriction of the sympathectomized pupil.

2. The frequency range of unit activity was from 0 to 28/sec. A maximal constriction of the pupil was maintained by unit activity in the region of 8/sec. The resting level of unit activity under chloralose anaesthesia was typically in the range 6–10/sec.

3. Stimulation in the defence area of the hypothalamus produced a maximal pupillodilation associated with a complete inhibition of unit activity and a block of the light reflex response.

4. Onset of retinal illumination produced a burst discharge followed by a transient silent period and then an over‐all increase in the rate of activity.

5. Cessation of retinal illumination produced a post‐excitatory depression of unit activity lasting from 190 to 700 msec. It is suggested that this effect is produced by retinal afferents activated by light ‘off’ that exert an inhibitory influence on the pupilloconstrictor neurones.
The form and distribution of the surface evoked responses in cerebellar cortex from intercostal nerves in the cat
Authors: Coffey G. L. , Godwin‐Austen R. B. , Macgillivray B. B. , Sears T. A.
Published: December 2014

1. The form and distribution of the cerebellar evoked responses to electrical stimulation of intercostal and other thoracic segmental nerves were investigated in anaesthetized cats.

2. Low intensity stimulation (< 2 × nerve threshold) evoked short latency, low amplitude (< 20 μV), initially surface positive responses which could only be distinguished with certainty from the electrocorticogram with averaging.

3. On the basis of experiments involving sectioning of afferent tracts it is concluded that intercostal evoked responses of less than 7·0 msec latency are conducted in dorsal spino‐cerebellar, ventral spino‐cerebellar and dorsal column (cuneo‐cerebellar) pathways.

4. The surface positive waves have a highly punctate distribution with a steep potential gradient extending over an area of about 1 mm diameter. It is postulated that these small fields represent activation of single or few mossy fibre inputs.

5. Short latency responses to thoracic inputs were found only in the ipsilateral intermediate cortex and lateral margin of the vermis of the anterior lobe (lateral two thirds of Larsell's lobules IV and V of the accessible cortex). The responses were distributed throughout the fore and hind limb areas of the anterior lobe and no rostro‐caudal or medio‐lateral segmental organization was seen.

6. It is suggested that the overlapping distribution of thoracic and fore and hind limb mossy fibre inputs within the cerebellar cortex provides an anatomical basis for the integration of information from the trunk and from the limbs.
The elastic constants of the human lens
Authors: Fisher R. F.
Published: December 2014

1. When the lens is spun around its antero‐posterior polar axis in an apparatus designed for the purpose, high speed photography can be used to record its changing profile. By this method a variable radial centrifugal force can be applied to the lens which mimics the pull of the zonule.

2. If the lens is not stressed at its centre beyond 100 Nm−2 it behaves as a truly elastic body. When stressed beyond this limit visco‐elastic strain is produced at its poles.

3. The human lens has isotropic elastic properties at the extremes of life, but at the other times Young's Modulus of Elasticity varies with the direction in which it is measured.

4. Young's Modulus of Elasticity of the lens varies with age, polar elasticity and equatorial elasticity, at birth being 0·75 × 103 and 0·85 × 103 Nm−2 respectively, while at 63 years of age both are equal to 3 × 103 Nm−2.

5. A comparison of Young's Modulus of the young human lens with that of the rabbit and cat shows that the polar elasticity of the lenses of these animals was 5 times greater in the young rabbit, and 21 times greater in the adult cat. Equatorial elasticities of the rabbit and human lens were equal, while in the cat the equatorial elasticity was four times greater.

6. A mathematical model showing the lens substance possessing a nucleus of lower isotropic elasticity than that of the isotropic elastic cortex surrounding it, accounts for the difference between polar and equatorial elasticity of the intact adult lens.

7. The implications of these findings are discussed in relation to:

(i) accommodation and the rheological properties of the lens;

(ii) possible differences in the physical state of the lenticular proteins in the cortex and nucleus which may account for the senile variations in Young's Modulus of Elasticity in these regions of the lens;

(iii) the loss of accommodation due solely to an increase in Young's Modulus of Elasticity of the lens between the ages of 15 and 60. This would amount to 44% of the total observed in vivo.
Optical studies on the kinetics of the sodium pump in mammalian non‐myelinated nerve fibres
Authors: Landowne D. , Ritchie J. M.
Published: December 2014

1. A study has been made of the changes in the fluorescence of desheathed rabbit cervical vagus nerves that occur during and after electrical stimulation of its non‐myelinated fibres.

2. Stimulation for 5 sec at 30 shocks/sec produces a maximal decrease, of about 1% of the resting fluorescence. Stimulation for less than 0·5 sec fails to produce responses visible above the inherent noise in the recording system.

3. A pharmacological dissection (with ouabain, metabolic inhibitors, and calcium) has revealed four phases of fluorescence change:

(a) under conditions where the sodium pump is functioning, there is a prolonged decrease in the fluorescence following electrical activity;

(b) even in the absence of pumping the mere entry of sodium into the nerve causes an initial decrease in fluorescence;

(c) the entry of calcium ions with electrical activity also causes an initial rapid decrease in fluorescence;

(d) following these phases of decreased fluorescence there is a phase of increased fluorescence.

4. These changes in fluorescence are related to changes in the NADH concentration in the nerve resulting from:

(a) the splitting of ATP during sodium extrusion;

(b) the initial binding of sodium to the sodium‐ and potassium‐dependent ATPase, which is the sodium pump;

(c) the stimulation of mitochondrial respiration by calcium that has entered during the spike; and

(d) an increased glycogenolysis as a result of the calcium entry during activity.
Electrical connexions between horizontal cells in the dogfish retina
Authors: Kaneko Akimichi
Published: December 2014

1. In dogfish, studies were made of electrical connexions between pairs of cells giving S‐potentials. After recording, the types and locations of the two cells were determined morphologically by electrophoretically injecting two different fluorescent dyes.

2. Hyperpolarizing S‐potentials were observed in external and internal horizontal cells; depolarizing responses were seen in bipolar cells. All pairs of external horizontal cells examined were electrically coupled, i.e. intra‐cellular polarization of one horizontal cell gave rise to polarization in its neighbour. Coupling was detected for cells separated by five other cells. The electrical coupling was non‐rectifying. No coupling was found between external and internal horizontal cells or between external horizontal cells and bipolar cells.

3. Generally the smaller the distance between cells, the larger the coupling ratio, but some pairs of cells separated by similar distances showed widely different coupling ratios.

4. The coupling between cells was also demonstrated by the finding that Procion Yellow injected into one external horizontal cell diffused into one or two neighbouring external horizontal cells. It did not diffuse into internal horizontal cells or bipolar cells.

5. Close membrane apposition has been reported between neighbouring external horizontal cells, but not between these and either bipolar or internal horizontal cells. The distribution of electrical connexions observed in the present study agrees with these anatomical findings.