bluuebunny/crossref_metadata_2025 huggingface dataset:
Rod‐dependent intracellular response to light recorded from the pigment epithelium of the cat retina
Authors: Schmidt Rainer , Steinberg Roy H.
Published: December 2014

1. Intracellular recordings from pigment epithelial cells reveal rod‐dependent hyperpolarizing responses to light which are identical with the c‐wave of the electroretinogram. These responses were studied as a function of the duration, intensity and area of light flashes and also were compared with rod‐dependent horizontal cell responses recorded under similar conditions.

2. Because of the long time constant of the response (800 msec), pigment epithelial responses increased in amplitude as flash duration was increased over a wide range. The response reached a plateau at a flash duration of 2·4 sec so that longer flashes only increased the duration of the response. Responses to repetitive flashes, even at a slow rate of 2/sec were integrated to produce a sustained voltage.

3. The growth of pigment epithelial response amplitude as a function of flash duration could be divided into two components. The increase in amplitude as flash duration was increased from 5‐50 msec was also observed in horizontal cells and was assumed to have originated in the rods. The growth in amplitude with longer flashes was unique to the pigment epithelial response.

4. The pigment epithelial response increased in amplitude as spot size was increased, reaching 90% of maximum with an 0·36 mm diameter spot. A precise measurement of the receptive field could not be obtained, because the responses were recorded in the tapetal area of dark‐adapted retinas. The b‐wave of the local electroretinogram which was ‘picked‐up’ intracellularly exhibited a much greater area effect.

5. Pigment epithelial responses increased in amplitude as flash intensity was increased but the amplitude‐log intensity functions differed as a function of flash duration. With long flashes (> 2·4 sec) the growth in amplitude was a power function of intensity (exponent = 0·6–0·7) and the response reached an amplitude ceiling at about 3·0 log td scotopic. At higher intensities the responses increased in duration (the rod after‐effect). With short flashes, e.g. 480 msec, the responses continued to increase in amplitude with flash intensity well above the intensity needed to produce amplitude‐ceilings for rod‐dependent responses. This additional increase in amplitude resulted from integration of the rod after‐effect by the pigment epithelial response.

6. Rod‐dependent horizontal cell responses followed the amplitude—log intensity functions that were recorded in pigment epithelial cells with long flashes. The rod after‐effect was also the same function of log intensity in both responses.

7. It was concluded that the pigment epithelial response is not generated by a late photoproduct. Rather, it appears to depend upon the same mechanism of rod excitation as the horizontal cell response, and the essential characteristics of both rod‐dependent responses originate in individual rods.
Incremental responses to light recorded from pigment epithelial cells and horizontal cells of the cat retina
Authors: Steinberg Roy H.
Published: December 2014

1. Rod‐dependent incremental responses were recorded intracellularly in both pigment epithelial cells and horizontal cells of the cat retina. They were elicited by test flashes which were superimposed on background flashes after a delay.

2. In pigment epithelial cells smaller test responses were produced as background intensity was raised. The incremental sensitivity function was linear for about 1·4 log units, with a slope of 0·86, and the approach of saturation occurred at about 2·5 log td scotopic.

3. The amplitude of pigment epithelial test responses could be estimated from the dark‐adapted amplitude—log intensity function obtained with single flashes. Test flashes produced the voltage increment predicted by the slope of this function just above the point on the curve equal to the background intensity. The pigment epithelial response to a test flash, therefore, is the response expected if the background were presented alone and made more intense by the amount of the test flash.

4. Rod‐dependent incremental sensitivity functions of horizontal cells closely resembled the ones obtained from pigment epithelial cells.

5. It was concluded that the adaptive effects observed in pigment epithelial cells originated in individual rods. These effects arose from the compressive nature of the dark‐adapted amplitude—intensity function. In horizontal cell responses these effects may be modified by the failure of the background response to maintain its initial voltage.
Switching of the respiratory phases and evoked phrenic responses produced by rostral pontine electrical stimulation
Authors: Cohen Morton I.
Published: December 2014

1. In midcollicular‐decerebrate, gallamine‐paralysed, vagotomized cats, efferent phrenic discharge was recorded as an indicator of the central respiratory cycle. Electrical stimulation (50–250/sec) delivered in the rostral lateral pontine ‘pneumotaxic centre’ region (in and near nucleus parabrachialis), and set to occur at specified times in the cycle, produced powerful respiratory effects: (a) at dorsolateral points, inspiratory‐facilitatory effects (increase of phrenic discharge, shortening of the expiratory phase); (b) at ventrolateral points, expiratory‐facilitatory effects (decrease of phrenic discharge, shortening of the inspiratory phase, lengthening of the expiratory phase).

2. At both inspiratory‐facilitatory and expiratory‐facilitatory points, a single stimulus delivered during the inspiratory phase produced a short‐latency (4–7 msec) reduction of phrenic discharge, followed by a wave of increased activity. The short latency of the response indicates the existence of paucisynaptic descending inhibitory pathways. Succeeding stimuli in a high‐frequency train produced alternating waves of evoked activity and depression; the form of the responses depended on stimulus frequency and on locus of stimulation.

3. At inspiratory‐facilitatory points, short stimulus trains (10–30 stimuli) of adequate strength delivered in the middle and late expiratory phase caused early termination of the phase (latency 100–300 msec) and switching to a complete inspiratory phase, in which the phrenic discharge pattern resembled that in a normal inspiratory phase. Similarly, adequate stimulus trains applied at expiratory‐facilitatory points during the middle and late inspiratory phase caused early termination of the phase and switching to a complete expiratory phase.

4. The threshold for occurrence of each type of phase‐switching response depended on stimulus current, frequency, number of stimuli, and time of stimulus delivery. As stimulus trains were delivered later in the phase, the threshold for switching to the succeeding phase was progressively reduced. Moreover, the nature of the evoked effects was a non‐linear function of stimulus characteristics: a small increase of stimulus efficacy changed the system's response from (a) moderate shortening of the phase or transient change in phrenic discharge, to (b) complete termination of the phase.

5. These results indicate that, as each respiratory phase progresses, there is a steady increase of excitability in systems which promote the onset of the succeeding phase. Further, the existence of a relatively sharp threshold for switching of the respiratory phases suggests that the phase transitions occur when critical levels of excitation and inhibition are reached synchronously in populations of respiratory neurones.
Responses of inferior collicular neurones of bats to tone bursts with different rise times
Authors: Suga N.
Published: December 2014

1. A study was made of the responses of single neurones in the inferior colliculus of bats to tone bursts with different rise times (or with different rates of amplitude increase) in order to determine whether the neurones were specialized for analysis of amplitude‐modulated sound, especially the rising phase in amplitude.

2. The response patterns of neurones which showed phasic on‐responses usually did not change with rise time, although the response patterns of some neurones changed from phasic on‐responses to inhibitory responses.

3. The thresholds of responses to tone bursts increased when the rise time was lengthened. The amount of increase greatly differed from neurone to neurone. For the excitation of neurones which showed a large increase in threshold, the stimulus amplitude should quickly increase in amplitude. For tone bursts with a short rise time, some neurones showed an upper‐threshold above which the sounds failed to excite them. The upper‐threshold usually disappeared when the rise time was lengthened. For the excitation of neurones which showed an upper‐threshold, the rate of amplitude increase and its extent were very important parameters.

4. Lengthening the rise time of a tone burst from 0·5 to 98 msec caused various types of change in the excitatory area. In some cases, there was a diminution of the area and, in others, there was an expansion of the area. Neurones showing these changes may be considered to be specialized for responding to tone bursts with either a rapid or slow increase in amplitude.

5. Changes with rise time occurred not only in the excitatory area, but also in the inhibitory area. The change in the inhibitory area of a given neurone, however, was not necessarily the same as that in the excitatory area.

6. The latency of response usually changed as a function of stimulus amplitude and rise time. In 26% of the neurones studied, however, the latency was relatively constant regardless of stimulus amplitude and rise time. Some of the latency‐constant neurones appeared to have properties suited for echo‐ranging.

7. The changes in excitatory area with rise time appear to involve neural inhibition and/or accommodation. Possible neural mechanisms for the changes in threshold, upper‐threshold and response pattern and the properties of latency‐constant neurones are discussed.
Vagal non‐adrenergic inhibition of guinea‐pig stomach
Authors: Beani L. , Bianchi Clementina , Crema A.
Published: December 2014

1. The effect of vagal and sympathetic stimulation on the mechanical and electrical activity (intracellular recording) of the body of the guinea‐pig stomach was investigated in vitro.

2. Following atropine, 1 × 10−6‐1 × 10−7 g/ml., vagal responses were reversed from excitatory to inhibitory.

3. Sympathetic blockade, produced by α‐ and β‐receptor antagonists and adrenergic neurone‐blocking agents, reduced or abolished sympathetic, but not vagal inhibition.

4. Hexamethonium (5 × 10−5 g/ml.) reduced vagal relaxation to 11–30% according to the stimulation rate. The residual response was maintained in the presence of 5‐hydroxytryptamine tachyphylaxis.

5. Many muscle cells were observed to be under the influence of both vagus and sympathetic nerves: the effect of sympathetic stimulation was always inhibitory in nature, but high stimulation rates were required. The effect of vagal stimulation was both excitatory and inhibitory even in the absence of atropine: low stimulation rates gave rise either to E.J.P.s (excitatory junctional potentials), often followed by spikes, or to I.J.P.s (inhibitory junctional potentials).

6. In some spontaneously firing cells the interruption of electrical activity produced by vagal stimulation at 2/sec and sympathetic stimulation at 20/sec was recorded for a long enough time to check the effect of guanethedine (5 × 10−6 g/ml.): the drug selectively blocked sympathetic inhibition.

7. The significance of the inhibitory non‐adrenergic transmitter, released by the intramural neurones activated by preganglionic vagal fibres, is discussed.
Projection from low‐threshold muscle afferents of hand and forearm to area 3a of baboon's cortex
Authors: Phillips C. G. , Powell T. P. S. , Wiesendanger M.
Published: December 2014

1. The precentral and postcentral banks of the Rolandic fissure of the arm area of the baboon's cortex have been probed to their depths with extracellular micro‐electrodes under nitrous oxide and oxygen anaesthesia, supplemented by minimal intravenous pentobarbitone or chloralose.

2. Afferent volleys were sent in from the deep (motor) radial nerve and the deep palmar (motor) branch of the ulnar nerve. Their entry into the central nervous system was timed at the dorsal root entry zone. The nerves were stimulated in continuity and the effects of stimuli below threshold for the motor axons were investigated.

3. Area 3a, in the depths of the postcentral bank, which is cytoarchitectonically transitional between areas 3 and 4, is the receiving area for afferent impulses from muscle.

4. Evoked potential waves and unitary discharges began 4 msec, and the majority of units discharged between 5 and 10 msec, after the afferent volley reached the dorsal root entry zone.

5. Similar responses were elicited by a brief pull (70 μ in 1 msec) or brief vibration (50 μ at 250–400 Hz) applied to the tendons of m. extensor digitorum communis.

6. No potential waves were evoked in area 4, even in the depths adjacent to area 3a, by muscle afferent volleys.
Rhodopsin kinetics in the human eye
Authors: Alpern M.
Published: December 2014

1. Rhodopsin has been measured by Rushton's method of reflexion densitometry in a retinal region 18° temporal to the fovea, using a wavelength of measuring light (555 nm) so far into the long wave part of the spectrum that possible blue absorbing intermediates (e.g. transient orange) do not interfere.

2. Rhodopsin was bleached by a strong light for 10 sec and then held steady by a weaker light. During a 10 sec bleach, no regeneration occurs and the rate of bleaching is proportional to the quantum catch. The proportionality constant is about 10−7 (td sec)−1.

3. From 2, the rate of photolysis at equilibrium produced by the steady light was calculated. Since conditions were at equilibrium, photolysis matched regeneration. It was found that the rate of generation was proportional to the amount of pigment still bleached. The proportionality constant was about 0·0025 sec−1.

4. It was found by several different methods that the constant in 3 is the same in the light or dark and hence regeneration occurs independently of bleaching.

5. Therefore, the results from bleaching and regeneration experiments can be combined to give the general equation [Formula: see text], where p is the fraction of rhodopsin, t is time in sec and I is the retinal illuminance.

6. This equation describes the results of partial bleaching and regeneration experiments under a variety of different exposure intensities of moderately long (at least 10 min) exposure durations.

7. The dark adaptation curve in a peripheral region of the rod monochromat's retina where there are few cones follows a simple exponential course over nearly 7 log10 units. Rhodopsin regeneration and log threshold for this region are described by the same curve with a time constant of about 400 sec. Each log unit fal in threshold is accompanied by 0·835% increase in rhodopsin. This time constant is in agreement with Rushton's (1961) finding, but appreciably longer than that reported by Ripps & Weale (1969a).

8. The Ripps & Weale result was, however, obtained by bleaching with a very short bright xenon flash (as they did). Under these conditions, blue absorbing intermediate(s) is (are) formed, the time constant of regeneration of rhodopsin is much faster than after long tungsten bleaches, and the kinetic equation is not valid.

9. The general equation, together with the relation found in 7, successfully accounts for results previously published by others of the effect of duration and intensity of bleaching on the recovery of rod threshold in the dark, provided only that more than 5% of the rhodopsin was bleached at the beginning of dark adaptation.
Catecholamine synthesis and excretion in rats exposed intermittently to cold
Authors: Bibbiani Cecilia , Viola-Magni Maria Pia
Published: December 2014

Previous findings have shown a turnover of nuclear DNA, a condition related to the functional activity of these cells, in the adrenal medullae of rats intermittently exposed to cold. Striking differences have been observed between various strains of rats, particularly Italico and Wistar rats.

In order to evaluate the function of the adrenal medullary cells, the content of catecholamines in the organ and their urinary excretion have been evaluated, with the fluorimetric method, in rats of Italico and Wistar strains kept at room temperature and exposed intermittently to cold. The results show that (i) at room temperature the levels of excretion are lower in Italico than in Wistar rats in spite of the equal amine contents of the adrenal medullae, (ii) the first exposure to cold causes a large increase in the urinary excretion and a decrease of adrenaline and noradrenaline content of the adrenal glands in both strains, (iii) after 3 days the catecholamine content in the organ was higher than normal in Wistar rats, whereas in the Italico strain it continued to decrease, and (iv) a new steady state at higher levels is reached after 20 days of exposure, when not only the catecholamine content but also the urinary excretion is equal in both strains.

These differences between the two strains of rats during intermittent cold exposure are discussed in relation to the behaviour of DNA.
Depression of the reflex tachycardia from the left atrial receptors by acidaemia
Authors: Harry J. D. , Kappagoda C. T. , Linden R. J. , Snow H. M.
Published: December 2014

1. The effects are described of an acidaemia, produced either by the inhalation of carbon dioxide or by an intravenous infusion of hydrochloric acid, on the reflex increase in heart rate which results from stimulation of the left atrial receptors in the anaesthetized dog.

2. The results show that during acidaemia the reflex increase in heart rate from stimulation of the left atrial receptors is reduced. The extent of the reduction is related to the degree of the acidaemia.

3. It is suggested that it is necessary to monitor and correct changes in the pH of arterial blood in experiments which involve reflex changes in heart rate, especially if the efferent pathway involves the sympathetic nerves.

4. It is also suggested that the occurrence of such an acidaemia in anaesthetized surgically traumatized animals may be a factor contributing to the variability in results from investigations involving reflex changes in heart rate in response to stimulation of the left side of the heart.
A new approach for determining the volume of cerebral extracellular fluid and demonstration of its communication with c.s.f
Authors: Friede Reinhard L. , Hu Kuo Hao
Published: December 2014

1. A new technique is presented for determining the volume of extracellular space in bowfin (Amia calva) brain during in vitro incubation. It consists of solving simultaneous equations which are applied to determine the volume of extracellular space as well as intracellular marker concentration. This technique allows for a better insight into the redistribution of marker between incubation medium and extracellular space as well as between extracellular and intracellular space.

2. Na+, K+ and Cl− equilibrated within 10–15 min between incubation medium and extracellular space. There was no evidence of a homoeostatic mechanism controlling the concentration of these ions in the extracellular fluid, which appeared to be in equilibrium with cerebrospinal fluid. The extracellular spaces of these ions were identical: Na+, 23·4; K+, 23·3 and Cl−, 23·2%.

3. Sorbitol equilibrated with the extracellular fluid within 45 min and indicated an extracellular space of 22·6%, nearly identical with that for electrolytes.

4. Vastly different ‘spaces’ were obtained for [3H]methoxy inulin, which equilibrated within 45 min with a 13% space and [14C]carboxyl inulin, which showed a 46% space value for only 30 min. The difference may be explained by marker decomposition. The 9% difference between the [3H]methoxy inulin and sorbitol spaces may be explained by a ‘packing’ factor attributable to molecular size.
Nucleus Z, the medullary relay in the projection path to the cerebral cortex of group I muscle afferents from the cat's hind limb
Authors: Landgren S. , Silfvenius H.
Published: December 2014

1. The medullary relay of hind limb muscle afferents was studied in cats anaesthetized with chloralose. Evoked potentials were recorded from the dorsal surface of the medulla oblongata and from the depth of the medulla with penetrating micro‐electrodes. Graded electrical stimulation of the muscle nerves was used. The afferent volley was monitored by recordings from the lumbar dorsal roots or from the peripheral nerves.

2. Group I muscle afferents from the ipsilateral quadriceps, posterior biceps‐semitendinosus and gastrocnemius‐soleus nerves evoked potentials in the nucleus Z of Brodal & Pompeiano (1957a). Focal and unitary potentials were recorded within 2·7–3·8 mm rostral to the obex and 2·8–4·1 mm lateral to the mid line. The recording positions were checked histologically.

3. Focal and unitary responses appeared at threshold strengths of the afferent volleys. The latencies of the focal potentials varied between 4·5 and 7·0 msec, those of the unitary ones between 5·1 and 11·0 msec. Group II muscle afferents and low threshold cutaneous afferents also projected to nucleus Z.

4. An antidromic discharge was evoked in the relay cells of nucleus Z by electrical stimulation of the contralateral thalamus.

5. A lesion of nucleus Z abolished the response evoked in the contralateral post‐sigmoid gyrus of the cerebral cortex by the Group I muscle afferents of the hind limb.

6. A superficial transection of the ipsilateral dorsolateral fascicle at the 1st cervical segment abolished the potentials evoked in nucleus Z.

7. Results of lumbar cord transections showed that most of the primary afferents of the Group I hind limb path supplying nucleus Z enter the dorsolateral fascicle at L3 level.

8. The relation of the Group I hind limb path to the dorsal spinocerebellar tract is discussed.
Responses of vibration‐sensitive receptors in the interosseous region of the duck's hind limb
Authors: Dorward Patricia K. , McIntyre A. K.
Published: December 2014

1. Responses of receptors with fibres in the interosseous nerve of the duck's leg have been studied by recording unit discharges in filaments dissected from the sciatic nerve.

2. Seventy‐two of the ninety‐four units examined served highly phasic, vibration‐sensitive mechanoreceptors in the interosseous region interpreted as being Herbst corpuscles. Receptor types for most of the other units could not be determined, but some were slowly adapting mechanoreceptors.

3. Rheobase threshold values for the most sensitive vibration‐receptors were similar to those of mammalian Pacinian corpuscles.

4. Threshold—frequency relationships for the vibration receptors showed a wider range of low frequency cut‐off values, and a greater capacity to signal high frequencies, than is the case with Pacinian corpuscles.

5. Fibres of the vibration‐receptors had calculated diameters ranging from 5 to 10 μm and account for the bulk of the larger fibres in the interosseous nerve.

6. It is suggested that Herbst corpuscles in the legs of birds might act as a warning device by detecting vibratory disturbances of the ground or other supporting surface.
Development of isometric tension in simian extraocular muscle
Authors: Fuchs A. F. , Luschei E. S.
Published: December 2014

1. Isometric tension resulting from electrical stimulation of the abducens nerve was measured in the lateral rectus muscle of anaesthetized monkeys.

2. The lateral rectus showed no increase in maximum tension at stimulus frequencies greater than 400/sec.

3. However, at frequencies between 400 and 600/sec, the rate of change of tension increased so that maximum tension was achieved more rapidly.

4. Rates greater than 600/sec caused no further increases in the rate of change of tension and actually resulted in a decrease of maximum tension.

5. Since, in addition, single fibre recordings from ocular motor nerves reveal maximum discharge rates of less than 600/sec, units in the abducens nucleus that fire at greater than 600/sec are likely interneurones.

6. Stimulation at rates of 30/sec, the frequency at which feline slow or slow twitch fibres produce fused contraction, produced no measurable tonic component of tension. Therefore, the force contributed by slow muscle fibres probably plays an insignificant role during eye movements.
Ultrastructure and contractures of the pigeon iris striated muscle
Authors: Pilar G. , Vaughan P. C.
Published: December 2014

1. The ultrastructure of adult pigeon iris muscle fibres has been described with emphasis on the distribution of the sarcoplasmic reticulum (SR). Contractures due to superfusion with solutions of different [K+] (3–150 m
M) and acetylcholine (ACh) and their modification by alteration of external [Ca2+] and [Mg2+] were studied in isolated pigeon iris.

2. The arrangement of the contractile myofilaments was like that of vertebrate skeletal fibres. The SR is well developed in the I‐band and sparse at the A‐band level.

Tubular elements (T‐system) which form triads with the SR were seen at all levels of the sarcomere though usually adjacent to the A—I junction.

3. K+ contractures developed monotonically to a steady level which was maintained for the duration of the high [K+] superfusion. The response to a standard [K+] stepwise change was not altered by conditioning the preparation with various [K+].

4. Decreasing external [Ca2+] from 20 m
M to Ca2+‐free (i.e. no Ca2+ added), enhanced iris contractures at all [K+] and in ACh enriched solutions. The K+ response was abolished when the iris was superfused with Ca2+ free solution plus EDTA (2 m
M) for 45 min. Increasing [Mg2+] had little or no effect on iris contracture.

5. Reducing external [Ca2+] from 3 to 0·3 m
M caused a reduction of 3‐7 mV in resting membrane potential and an increase from 3 to 10 m
M‐Ca2+ caused 3 to 7 mV membrane hyperpolarization. Muscle fibre input resistance was not affected.

6. It is concluded that in the pigeon iris, Ca2+ required for contractile activation is obtained from internal stores, that membrane potential determines the degree of contractile activation and that the maintenance of the contracture is dependent on the failure of the Ca2+ releasing mechanism to inactive. In addition, it is speculated that because the iris muscle has only sparse SR at the A‐band level of the sarcomere, there may be slow Ca2+ reaccumulation.
Afferent discharges from arterial mechanoreceptors in the kidney of the rabbit
Authors: Niijima Akira
Published: December 2014

1. Afferent discharges were observed in dissected filaments or single nerve fibres of renal nerves in the rabbit.

2. Increasing the arterial perfusion pressure in excised kidney preparations caused an increase in afferent discharge rate. Increasing the venous pressure was without effect. Receptor discharge patterns were compatible with those of the slowly adapting type.

3. In vivo, increasing the systemic blood pressure by means of the sinus reflex caused an increase in afferent discharge rate. Afferent discharge patterns showed no synchronicity with heart beat, irrespective of the blood pressure levels.

4. It is suggested that mechanoreceptors are present around the arterial walls in the kidney and that they send information about blood pressure levels in the renal artery to the central nervous system.
The action of phospholipases on the inner and outer surface of the squid giant axon membrane
Authors: Abbott N. Joan , Deguchi T. , Frazier D. T. , Murayama K. , Narahashi T. , Ottolenghi A. , Wang C. M.
Published: December 2014

1. The effects of phospholipases on resting potential, action potential and membrane ionic conductances of squid giant axons have been studied by means of internal perfusion and voltage clamp techniques. The sample of phospholipases used exhibited both phospholipase A and B activities.

2. When applied externally, phospholipases had no effect on the resting and action potentials at a concentration of 100 μg/ml.

3. When applied internally, the enzymes effectively suppressed the amplitude and maximum rate of rise of the action potential at a concentration of 100 μg/ml. The resting potential started decreasing appreciably only after the action potential had been suppressed to a considerable extent.

4. Under voltage clamp conditions, the peak transient current was suppressed following internal perfusion of phospholipases, 150 μg/ml. The steady‐state current began to decrease, and the leakage current to increase only after the transient current had been suppressed to a considerable extent.

5. The time course of sodium inactivation was not significantly slowed by internal perfusion of the enzymes.

6. The curve relating the peak transient conductance to the membrane potential was shifted in the direction of depolarization after internal perfusion of phospholipases. No appreciable shift of the steady‐state conductance curve was observed.

7. These experimental results are discussed in connexion with the possible role of membrane phospholipids in the conductance changes associated with excitation.
The depolarizing action of acetylcholine or carbachol in intestinal smooth muscle
Authors: Bolton T. B.
Published: December 2014

1. The membrane potential of the longitudinal muscle of the guinea‐pig ileum was recorded intracellularly with glass micro‐electrodes.

2. Acetylcholine or carbachol depolarized the membrane. The depolarization produced by 1·4 × 10−6
M carbachol was only 3·6 mV less than that produced by 5·5 × 10−5
M.

3. When the change in size of the electrotonic potential was used to estimate the increase in membrane conductance produced by different concentrations of carbachol, the increase in conductance was about tenfold at 1·4 × 10−6
M and about 100‐fold at 5·5 × 10−5
M. There was a significant (P < 0·025) regression of the change in size of the electrotonic potential on the logarithm of the concentration of carbachol over this dose range. This and other observations suggest that it is not the availability of receptors which curtails the depolarization produced by concentrations of carbachol in excess of 1·4 × 10−6
M.

4. Reducing the external sodium concentration shifted the level of peak depolarization produced by carbachol negatively, and increasing the external sodium concentration shifted it positively.

5. Reducing the external chloride from 134 to 13 m
M had no significant effect on the level of peak depolarization produced by carbachol. Reducing the external chloride to 7 m
M shifted the level of peak depolarization 3·1 mV in a positive direction.

6. Increasing the external potassium concentration had little effect on the level of peak depolarization produced by carbachol, and decreasing the external potassium shifted the level of peak depolarization positively.

7. It was possible to account for the observed relationship between membrane potential and membrane conductance if the assumption was made that carbachol opens additional ion channels in the membrane which have an equilibrium potential of about −9 mV. It is suggested therefore that the depolarizing action of carbachol on this smooth muscle is limited by its equilibrium potential, and that the equilibrium potential and the membrane potential in the presence of large concentrations of carbachol (e.g. 5·5 × 10−5
M) are very close. Hence changes in the level of peak depolarization produced by varying the ionic composition of the external solution probably reflect changes in the equilibrium potential fairly closely.

8. A simple model in which carbachol opens conductances to sodium, potassium and chloride ions and in which these conductances are independent of external ion concentrations (and voltage) could account for the effects on the equilibrium potential of varying [Na+]0 and [Cl−]0 but not [K+]0.

9. It is suggested that carbachol increases the conductance to sodium, potassium and possibly other cations, and that, if it increases chloride conductance, then the increase produced is small relative to the increase in conductance to cations.
Site of action of 2‐deoxy‐D‐glucose mediating gastric secretion in the cat
Authors: Kadekaro Massako , Timo‐Iaria C. , Valle L. E. R. , Velha L. P. E.
Published: December 2014

1. Site of action of 2‐deoxy‐
D‐glucose (2‐DG) responsible for its effect on gastric secretion was investigated in cats prepared with polyethylene or nylon cannulae chronically implanted in the antrum.

2. The patterns of their basal secretion and secretory response to slow intravenous administration of 60 mg 2‐DG/kg body wt. were determined. After being subjected to selective neural lesions the cats were tested again and the secretory response was compared with the control.

3. The normal response to 2‐DG in the cat is equivalent to that obtained in the dog. Volume, pH, acid concentration and output, chloride concentration and pepsin output attain peak values in 45–60 min.

4. After intercollicular transection of the mid‐brain no secretory response occurred except for a tendency of acid concentration to increase. Large lesions of several diencephalic structures did not suppress the secretory response. Only those cats with a circumscribed lesion of the lateral area of the medial and posterior hypothalamus were unresponsive to 2‐DG. Acid secretion, as in the decerebrate animals, showed a slight tendency to increase after 2‐DG. Lesions immediately rostral, medial and dorsal to the territory of the medial forebrain bundle were ineffective in preventing augmentation of secretion. Destruction of structures contributing fibres to the medial forebrain bundle at hypothalamic levels, such as the neocortex, amygdala, fornix, septal and preoptic areas, did not change the secretory response.

5. Intrafascicular neurones of the medial forebrain bundle are suggested as the main site of action of 2‐DG on gastric secretion.
Degeneration of sympathetic nerves in vitro and development of smooth muscle supersensitivity to noradrenaline
Authors: Geffen L. B. , Hughes Chris C.
Published: December 2014

1. The sequence of events involved in degeneration of sympathetic nerve terminals has been studied in vitro in the expansor secundariorum muscle of the chicken.

2. The muscle underwent a degeneration contraction due to abrupt release of noradrenaline stores from the nerves about 18 hr after isolation. The tension reached its peak within 6 hr at about 44% of the maximum tension developed to added noradrenaline.

3. Responses to nerve stimulation were transiently potentiated by 35% on average just before the onset of the degeneration contraction and then failed abruptly.

4. Degeneration release of noradrenaline was Ca2+‐dependent. Development of the degeneration contraction was delayed by temporary withdrawal of Ca2+ from the medium and was accelerated by a twofold increase in Ca2+ concentration when applied at a critical period close to the onset.

5. Neither continuous nerve stimulation nor alterations in the length of the nerve stump influenced the course of the degeneration contraction in vitro.

6. When the muscle was left in situ after denervation, the degeneration contraction occurred between 2 and 3 days later depending on the length of the distal portion of nerve. Cutting the nerve supply 5 cm closer to the muscle in vivo hastened the loss of transmission and the onset of the degeneration contraction by 24–48 hr.

7. Supersensitivity to noradrenaline occurred soon after the degeneration contraction but the full development of a sevenfold supersensitivity to noradrenaline, equivalent to that produced by cocaine, took up to 48 hr. No further increase in sensitivity to noradrenaline could be detected in vitro after chronic denervation in vivo for up to 30 days.

8. It is concluded that the degeneration contraction and failure of transmission was precipitated by an abrupt increase in the Ca2+ permeability of the axon causing discharge of transmitter from vesicles. This was probably the result of depletion of essential factors normally transported somatofugally in the axon at 1–2 mm/hr. The supersensitivity to noradrenaline that develops subsequently appears to be due to a loss of the uptake mechanism of the nerve terminals.
The role of post‐synaptic neurones in the biochemical maturation of presynaptic cholinergic nerve terminals in a mouse sympathetic ganglion
Authors: Black I. B. , Hendry I. A. , Iversen L. L.
Published: December 2014

1. The role of post‐synaptic adrenergic neurones in the biochemical maturation of presynaptic cholinergic nerve terminals has been investigated in mouse superior cervical ganglion in vivo.

2. Selective destruction of ganglion adrenergic neurones chemically, with 6‐hydroxydopamine (6‐OH‐DA), or immunologically, with nerve growth factor antiserum (NGF‐antiserum) prevented the normal maturation of choline acetyl transferase (ChAc) activity in presynaptic endings during development. Enzyme activity remained depressed for at least 2 months.

3. 6‐OH‐DA treatment failed to alter ChAc activity in the developing duodenum or diaphragm, organs in which cholinergic fibres do not synapse with adrenergic neurones, suggesting that destruction of post‐synaptic neurones per se inhibited presynaptic maturation.

4. Similarly, NGF‐antiserum, which does not destroy adrenergic neurones in the adult did not alter ChAc activity in adult mouse ganglia.

5. These observations suggest that post‐synaptic adrenergic neurones regulate the biochemical development of presynaptic cholinergic nerve terminals.
An analysis of volume changes in the T‐tubes of frog skeletal muscle exposed to sucrose
Authors: Birks R. I. , Davey D. F.
Published: December 2014

The volume responses of the T‐system of frog skeletal muscle to isotonic solutions of altered ionic composition, as studied by electron microscopic examination of osmium‐fixed tissue, have been re‐investigated using aldehyde fixatives.

1. In confirmation of the earlier work we find that the T‐tubes swell in frog sartorius muscles which have been soaked in Ringer solution in which the sodium chloride concentration has been reduced to 40 m
M and tonicity maintained with sucrose before fixation in osmium.

2. The swelling does not occur in muscles similarly treated, but fixed with acrolein or glutaraldehyde.

3. Swelling of the T‐tubes, which has been reported for osmium‐fixed muscle following exposure to Ringer in which chloride is replaced by acetate, or reduced and sulphate substituted, does not occur when fixation is by acrolein.

4. Analysis of the data from the earlier work with sucrose substitution shows that the degree of T‐tube swelling is proportional to the sucrose concentration of the soaking medium, whether the solution be isotonic or anisotonic.

5. It is concluded that the increase in T‐tube volume arises in muscles which have been exposed to certain impermeant solutes during fixation by osmium, and a possible mechanism to account for the effect is described.

6. The relevance of these observations to the hypothesis that the sarcoplasmic reticulum is an extracellular compartment in muscle and to the proposal that the T‐tubes may represent an intermediate compartment for potassium fluxes is discussed.
The effects of bile salt and raw bile on the intestinal absorption of micellar fatty acid in the rat in vitro
Authors: Rampone Alfred J.
Published: December 2014

1. The uptake, esterification and transport of [14C]oleic acid were studied using sacs of rat everted small intestine incubated in 25 ml. of a buffered mixture of sodium taurocholate, glyceryl mono‐oleate and 14C‐labelled oleic acid in micellar form.

2. Intestine obtained from bile fistula rats (bile duct cannulated 48 hr previously) showed elevated rates of 14C uptake into the tissue total lipid compared with sham‐operated controls.

3. Nearly all of the excess 14C uptake in the bile fistula group was in the form of free fatty acid. Both groups showed similar rates of [14C]oleic acid incorporation into tissue triglyceride and also similar, though small, amounts transported into the serosal fluid.

4. In further experiments using intestine from bile fistula rats the addition of 1 ml. of fresh rat bile to the incubation mixture reduced the 14C uptake to approximately control levels. The addition of 2‐3 ml. of fresh bile similarly reduced the uptake and increased 14C incorporation into the triglycerides of mucosal tissue and serosal fluid.

5. These responses were not entirely the result of the bile salts contained in fresh bile since increasing the taurocholate concentration per se caused uptake, esterification and transport all to increase. In the presence of the higher taurocholate concentration the addition of fresh bile still caused a decrease in 14C uptake.

6. There was no significant effect of either fresh bile or taurocholate on the transport of the 3‐O‐methyl analogue of
D‐glucose under comparable conditions.

7. It is concluded that raw bile contains one or more components other than bile salts which may be important in determining fatty acid absorption.
Eating caused by 6‐hydroxydopamine‐induced release of noradrenaline in the diencephalon of the rat
Authors: Evetts K. D. , Fitzsimons J. T. , Setler Paulette E.
Published: December 2014

1. Although it is well established that exogenous noradrenaline injected into the diencephalon causes the satiated rat to eat, it is not known whether eating may be induced by release of endogenous diencephalic noradrenaline. In the present experiment 6‐hydroxydopamine was injected into the diencephalon of the rat to release catecholamines and produce degeneration of catecholamine‐containing neurones.

2. Injection into the preoptic area of 0·01–16·0 μg of 6‐hydroxydopamine caused satiated rats to eat.

3. All doses of 6‐hydroxydopamine above 0·01 μg produced long‐lasting partial depletion of noradrenaline and dopamine in the region of the brain composed of septum, preoptic area and hypothalamus.

4. Repeated injections of 8 μg 6‐hydroxydopamine at intervals of several days caused progressively less eating.

5. Eating in response to 6‐hydroxydopamine was inhibited by pre‐treatment with desmethylimipramine, or by pre‐treatment with the adrenergic blocking agents phentolamine or MJ‐1999.

6. Water intake after 6‐hydroxydopamine was reduced by pre‐treatment with desmethylimipramine or MJ‐1999 but was enhanced after pre‐treatment with phentolamine.

7. It is concluded that release of diencephalic catecholamines by injection of 6‐hydroxydopamine causes eating in rats and that the catecholamine responsible for eliciting eating is noradrenaline.
The initiation of platelet thrombi in normal venules and its acceleration by histamine
Authors: Begent Nicola A. , Born G. V. R. , Sharp D. E.
Published: December 2014

1. In cheek pouch preparations of anaesthetized hamsters, platelet thrombi or ‘white bodies’ were produced in venules by the micro‐ionto‐phoretic application of adenosine diphosphate (ADP). Currents of 10–400nA were passed through micropipettes containing 10 m
M‐ADP, the tips of which were less than 5 μ from the outer wall of the venule. The effect was quantitated by determining the time between starting the currents and the first appearance of platelets adhering inside the venule opposite the tip of the micropipette.

2. Repeated applications of ADP to the same site on a venule caused the appearance of white bodies after intervals which were almost constant for up to 3 hr.

3. The time to first appearance of a white body was inversely related to the iontophoretic current between about 10 and 200 nA. Currents smaller than 10 nA had no effect on the platelets. With currents of 200 nA or more the time remained at a minimum of less than 20 sec.

4. With currents of about 300 nA the minimum time increased little as the pipette tip was withdrawn up to 20 μ from the venule; with greater distances the time increased progressively.

5. Histamine caused gaps to appear between endothelial cells in cheek pouch venules. Histamine at a concentration of 10 m
M in micropipettes was applied iontophoretically by currents of 300 nA to venules at the same sites as ADP. Histamine alone had no effect on circulating platelets. When applied before and together with ADP, histamine decreased the time to first appearance of white bodies by up to 40% below that determined with ADP alone. Iontophoretically applied histamine did not alter the mean blood flow velocity in the venules.

6. After stopping the application of histamine, the time to first appearance of white bodies produced by ADP increased again in about 5 min to the control values.

7. Bradykinin, which does not cause endothelial gaps in cheek pouch venules, did not accelerate the induction of white bodies like histamine.

8. There were no microscopic abnormalities in venules in which white bodies had formed. Venules exposed to histamine accumulated circulating carbon particles in discrete wall areas.

9. It is concluded that adhering white bodies can be induced repeatedly in normal venules by direct action of externally applied ADP on circulating platelets and that the accelerating effect of histamine on white body formation is due to the separation of endothelial cells which accelerates the inward diffusion of ADP.
Release of 5‐hydroxytryptamine from caudate nucleus and septum
Authors: Holman R. B. , Vogt Marthe
Published: December 2014

1. The anterior horn of one lateral ventricle was perfused in anaesthetized cats treated with inhibitors of monoamine oxidase, and the effluent was tested for 5‐hydroxytryptamine (5‐HT).

2. The basal release of 5‐HT varied from 0·25 to 4 ng in 25 min, and was usually about 1 ng.

3. The basal release rose and fell with body temperature.

4. Electrical stimulation for 15 min of the nucleus linearis intermedius or of the nucleus linearis rostralis caused a release of 5‐HT which rarely outlasted the collection period of 25 min.

5. Low frequencies (0·5/sec) were, per stimulus, more effective than high frequencies in releasing 5‐HT. Over a 15 min period of stimulation, however, the highest total yield was at 20/sec; it fell abruptly at still greater frequencies.

6. No release was obtained if the stimulating electrode was positioned in a variety of brain structures outside the two linear nuclei.

7. The experiments indicate that 5‐HT acts as a transmitter of impulses in neurones originating in the linear nuclei and terminating in caudate nucleus and septum.
The functional organization of the isthmo‐optic nucleus in the pigeon
Authors: Holden A. L. , Powell T. P. S.
Published: December 2014

1. Extracellular single unit records were taken from the isthmo‐optic nucleus of the pigeon, locating the nucleus by the antidromic field potential resulting from electrical stimulation of the isthmo‐optic tract.

2. Visual receptive fields were investigated for 248 units, and were classed into three types: directionally selective, directionally non‐selective, and posterior minimum. They ranged from 3 to 10° in extent.

3. The topographical representation of the visual field in the nucleus was investigated by histological verification of electrode tracks, and a correlation with the receptive field sequences. Vertical descent through the nucleus resulted in an upwards progression of receptive field locations. Lateromedial passage through the nucleus resulted in a forwards progression of receptive field locations.

4. The representation of the lower visual field is greater than that of the superior visual field: that for the central parts of the inferior field is greater than that for the periphery, and the representation of the anterior inferior quadrant is greater than that of the posterior inferior quadrant.