bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuronal pathway of the recurrent facilitation of motoneurones
Authors: Hultborn H. , Jankowska Elżbieta , Lindström S. , Roberts W.
Published: December 2014

1. The recurrent facilitation of motoneurones is a disinhibition, i.e. a release of the motoneurones from a sustained hyperpolarization evoked by tonically active inhibitory interneurones. Only two groups of interneurones are known to receive recurrent inhibition from motor axon collaterals via Renshaw cells; the interneurones mediating the reciprocal Ia inhibition and the Renshaw cells themselves. The properties of these two groups of neurones were studied to determine if they could produce the tonic inhibition of motoneurones removed during recurrent facilitation.

2. It was found that the tonic firing of Ia inhibitory interneurones is sensitive to anaesthetics to the same degree as is recurrent facilitation. The range of frequencies of tonic discharges of Renshaw cells appeared to be similarly low in unanaesthetized and anaesthetized preparations although in individual cells the discharge rates were decreased by anaesthesia.

3. The recurrent inhibition of Ia interneurones inhibiting a given group of motoneurones and the recurrent facilitation of the same group of motoneurones were, as a rule, evoked from the same nerves, although in some cats the origin of the recurrent facilitation was somewhat wider. In contrast no evidence could be found that the Renshaw cells which inhibit a functional group of motoneurones are inhibited by volleys in the nerves from which recurrent facilitation is regularly evoked.

4. It was concluded that the recurrent facilitation is caused mainly by inhibition of the tonic activity of Ia inhibitory interneurones and that it is thus a manifestation of the recurrent control of Ia reciprocal inhibition of motoneurones.
The independence of electrogenic sodium transport and membrane potential in a molluscan neurone
Authors: Marmor Michael F.
Published: December 2014

1. The current—voltage relations of the Anisodoris giant neurone (G cell) were studied in the presence and absence of Na pump activity.

2. Inhibition of the electrogenic Na pump with ouabain had no effect on either the presence at warm temperatures (10–15° C), or absence at cold temperatures (0–5° C), of inward‐going rectification.

3. Abolition of inward‐going rectification in the warm, by replacement of external K with Rb, did not affect the electrogenic Na pump.

4. The current generated by the electrogenic pump was essentially constant between the membrane potentials of — 30 and — 100 mV.

5. The potential produced by the electrogenic pump can be predicted by a modification of the constant field equation.

6. It is estimated that the energy required to extrude Na was between 3160 and 3700 cal/g‐atom, and that uncoupled Na efflux during pump activity was typically between 0·2 and 4·0 p‐mole/cm2.sec.
Maternal hyperventilation and foetal hypocapnia in sheep
Authors: Baillie P. , Dawes G. S. , Merlet Claudie L. , Richards R.
Published: December 2014

1. In anaesthetized foetal lambs near term, hypocapnia induced by maternal hyperventilation abolished the rise of arterial pressure and femoral vasoconstriction caused by hypoxaemia. This is consistent with interaction of PCO2 and PO2 on the foetal aortic bodies.

2. In immature lambs (0·6−0·77 of term) maternal hyperventilation caused a fall in foetal carotid PCO2 commensurate with that in the maternal blood. In mature lambs (at 0·9 or more of term) the fall in foetal carotid PCO2 was less than that in maternal blood, whether the foetus was exteriorized or in utero.

3. The mean transplacental gradient for PCO2 (maternal arterial‐umbilical vascular), when the foetus was replaced with a mechanical pump recirculating foetal blood, was 6·3 mm Hg. This is attributed to placental CO2 production, and is nearly half the mean PCO2 gradient (maternal artery‐foetal carotid) of about 14 mm Hg during normal maternal ventilation.

4. The mean maternal‐umbilical transcotyledonary venous gradients (avoiding vascular shunts through the myometrium and intercotyledonary chorion) were for PCO2 1·7 mm Hg and for PO2 13·4 mm Hg.

5. Maternal hyperventilation (Pa, CO2 ∼ 20 mm Hg) caused a small fall in mean foetal carotid PO2 (5 mm Hg), which was readily reversible with no evidence of progressive acidaemia.
The action of carbon dioxide on afferent transmission in the dorsal column—lemniscal system
Authors: Morris Mary E.
Published: December 2014

1. Transmission in the lemniscal afferent pathway was studied in thirteen decerebrate, unanaesthetized cats while changing the concentration of inspired PCO2.

2. 2‐20% CO2, when inhaled for ≤ 10 min, raised the mean tissue PCO2, recorded from the surface of the medulla or cerebellum, from 22 torr to between 26 and 93 torr.

3. Medial lemniscal potentials were evoked by stimulation of a forelimb nerve and recorded from the transected surface of the contralateral mid‐brain. The transmission of supramaximal responses was progressively and reversibly depressed as tissue levels of PCO2 were raised and lowered. The time course of the changes in transmission corresponded closely to changes in the tissue PCO2.

4. The amplitude of the main early lemniscal peak was decreased to 80% by the inhalation of 20% CO2. A late component of the lemniscal response, presumably due to repetitive firing and conduction in smaller fibres and polysynaptic pathways, was more affected than the early main response.

5. The failure of transmission was unrelated to threshold changes in the peripheral nerve, since potentials recorded close to the site of stimulation showed no changes.

6. Increases in the transmission time of the main lemniscal potentials were uniform and < 10% during the administration of CO2 and did not appear to contribute to amplitude changes.

7. The inhibition of afferent transmission from one nerve by a preceding conditioning volley in a second nerve was not altered by hypercarbia.

8. It is concluded that CO2 has a blocking action on afferent transmission in the pre‐thalamic lemniscal system. The site of this block may be at the synapses and/or other regions of low safety factor in the afferent fibres.
The origin of the basal cell potential in frog corneal epithelium
Authors: Akaike Norio
Published: December 2014

1. As the micro‐electrode penetrated through the epithelial cell membranes of frog cornea, a stepwise increase in the potential reaching a maximum value of — 60 mV (‘basal cell potential’) was observed. Upon penetrating the stroma, the potential dropped abruptly but remained negative (‘stroma potential’).

2. The basal cell potential was determined as a K+ or a Cl− electrode, but the cell membrane was far more permeable to Cl− than to K+. It was also permeable to Na+, but to a smaller extent.

3. When the product [K]o.[Cl]o was kept constant, for a tenfold increase in [K]o the slope of the basal cell potential approached 58 mV at high [K]o. The slope was greater in the excised cornea than in the whole eye.

4. The basal cell membrane was more permeable to SCN− than to Cl−. Its selectivity towards cations was in the order K+ > Rb+ > Cs+ > NH4+.

5. In Li+ solution the basal cell membrane in the excised cornea caused a hyperpolarization, followed by a gradual depolarization. In contrast, a slow progressive hyperpolarization occurred in the whole eye.

6. Ouabain applied to the epithelial surface of both kinds of preparations did not affect the basal cell potential, but the potential was reduced when applied to the endothelium. MIAA and FDNB also depolarized when applied to both sides of the basal cell.

7. With 90 m
M‐K+ solution containing Cl− or CH3SO4− applied to the epithelial surface, the potential change occurred only in the high K+ solution with CH3SO4−.

8. The significance of these results for understanding the role of the epithelial boundary regulating the influence of Na+, K+, Cl− and drugs is discussed.
Frequency—response analysis of central vestibular unit activity resulting from rotational stimulation of the semicircular canals
Authors: Jones G. Melvill , Milsum J. H.
Published: December 2014

1. The neural response of semicircular canal‐dependent units in the vestibular nuclei of cats has been examined over a frequency range of sinusoidal rotation extending from 0·004 to 0·9 Hz.

2. Frequency—response analysis indicates that, over the range examined, the information contained in the neural signal received by the brain stem was similar to that expected from the mechanical end‐organ.

3. Over the experimental frequency range, the relation between neural response and mechanical stimulus was found to be dominated by a single time constant of about 4 sec, such that two response regions can be defined above and below a stimulus frequency of ¼ rad/sec (≃ ≃ Hz).

4. Above this frequency the information content of the neural signal tends towards that of angular velocity and below that frequency it tends towards that of angular acceleration.

5. It is inferred (a) that the so‐called ‘long’ time constant of the cat's horizontal canal is about 4 sec and (b) that during most normal head movements containing frequencies below about 1 Hz the informational mode of neural signals generated in the canal and received in the brain stem probably tends towards that of head angular velocity.

6. This seems appropriate for the generation of vestibulo‐ocular reflex compensation for head movement and for reflex damping (negative velocity feed‐back) of unintended head and body movements.

7. The average neural gain of central unit responses is estimated at 1264 action potentials/sec, per degree of cupular deflexion. This high value reflects the very small angles of cupular deflexion assessed on the basis of physical characteristics of the canal.

8. The results permit a rough estimate of the elastic restoring coefficient of the cupula in the horizontal canal as 2·05 × 10−3 dyne. cm.
Excitation—contraction coupling in amphioxus muscle cells
Authors: Hagiwara S. , Henkart Maryanna P. , Kidokoro Y.
Published: December 2014

1. Excitation‐contraction coupling was studied in myotomal muscles of amphioxus, Branchiostoma californiense.

2. The action potential of a muscle cell produces a twitch with a rise time of 30–40 msec at 11° C and its Q10 is about 2·2.

3. The twitch increases in amplitude with increasing external Ca concentration and is abolished in Ca‐free saline (1 m
M‐EGTA and 55·7 m
M‐MgCl2); the twitch amplitude is suppressed by Co or La ions.

4. Caffeine at concentrations above 1 m
M in the external saline causes a prolongation of the action potential and a contracture which lasts several minutes.

5. After exposure to caffeine the responsiveness of the muscle to subsequent applications of caffeine recovers in normal saline in 20–30 minutes but not in Ca‐free saline.

6. The amplitude of the caffeine contracture is independent of the external Ca concentration and is unaltered after the twitch is eliminated in Ca‐free saline.

7. After exposure to caffeine a full‐sized twitch can be obtained before the responsiveness to caffeine shows any significant recovery.

8. It is concluded that the twitch is produced by the Ca influx resulting from the increased permeability of the muscle cell membrane to Ca during the action potential and that the Ca mobilized by caffeine is not necessary to the initiation of the twitch.

9. Electronmicroscopy shows the existence of sarcoplasmic reticulum.
Central neural regulation by adrenergic nerves of the daily rhythm in hepatic tyrosine transaminase activity
Authors: Black Ira B. , Reis Donald J.
Published: December 2014

1. In adrenalectomized fasted rats transection of the spinal cord at C7‐C8 or placement of bilateral electrolytic lesions in the lateral hypothalamus when performed in the morning interrupted the daily rhythm of hepatic tyrosine transaminase by elevating low (AM) enzyme activities to high (PM) levels; lesions placed in PM did not affect the late afternoon rise in enzyme activity.

2. Bilateral thalamic lesions had no affect on enzyme activity.

3. The activity of hepatic catechol‐O‐methyl transferase was unaffected by hypothalamic lesions.

4. The lesion‐evoked rise of tyrosine transaminase activity was abolished by exogenously administered norepinephrine.

5. Cycloheximide blocked the rise of tyrosine transaminase activity caused by hypothalamic lesions.

6. The results suggest that rhythmic activity of sympathetic nerves governed by lateral hypothalamus contribute to regulation of the daily rhythm in tyrosine transaminase by regulating the release of norepinephrine peripherally; norepinephrine may block the daily rise of enzyme by interfering with protein synthesis, possibly of new enzyme, by competing with pyridoxal co‐factor.

7. It is proposed that alternating activity of sympathetic‐adrenergic and vagal‐cholinergic nerves to liver, controlled by the
C.N.S., contribute to rhythmic activity of hepatic tyrosine transaminase.
The mechanical properties and heat production of chicken latissimus dorsi muscles during tetanic contractions
Authors: Canfield S. P.
Published: December 2014

1. A study has been made of the mechanical properties and heat production of chicken anterior (ALD) and posterior (PLD) latissimus dorsi muscles during contractions at 20 °C.

2. There is a difference between these two muscles in the time course of the isometric response. The PLD reaches maximum tetanic tension 10 times faster and relaxes 8 times faster than ALD. The ratio of heat rate to isometric tension (heat rate/tension × length) for PLD is 7–8 times larger than for ALD.

3. ALD maintains substantial isometric tension for more than 2 min of stimulation. In PLD tetanic tension begins to fall after only 1 sec.

4. The ALD muscle does not show the ‘activation’ heat seen at the start of contraction with frog and toad muscle but this may be present in PLD.

5. There is a range of stimulation frequencies for both muscles over which the fused tetanic tension increases with stimulation frequency.

6. The tension—length curve of ALD has a pronounced plateau and is broader than that of PLD.

7. The normalized force—velocity relations for the two muscles are similar and may be fitted by Hill's equation with a value of a/P0 = 0·15–0·16. The maximum velocity of unloaded shortening of PLD is 4‐5 times that of ALD.

8. Preliminary experiments indicate that the resting heat rate of both muscles is 4 times greater than that of frog muscle at the same temperature. The recovery heat rate of ALD is similar to that of frog.
Mechanisms relating gastric acid secretion and mucosal blood flow during gastrin and histamine stimulation
Authors: Reed J. D. , Smy J. R.
Published: December 2014

1. Gastric mucosal blood flow (MBF) and gastric acid secretion have been compared and related during the infusion of a wide dose range of gastrin extracts, pentapeptide (Peptavlon, I.C.I. 50123) and histamine.

2. Constancy of increase in mucosal blood flow relative to H+ secretion was obtained with gastrin stimulation, whereas histamine stimulation produced higher ratios of mucosal blood flow to H+ secretion, and these ratios declined as each experiment continued.

3. The importance of considering only the increase in mucosal blood flow in relation to acid secreted is demonstrated.

4. It is concluded that the differences shown in the ΔMBF/ΔH+ with histamine and gastrin stimulation provide further evidence that the amidopyrine clearance technique measures gastric mucosal blood flow.
The activity of identified supraoptic neurones and their response to acetylcholine applied by iontophoresis
Authors: Dreifuss J. J. , Kelly J. S.
Published: December 2014

1. In urethane/pentobarbitone anaesthetized male rats, the hypothalamus and pituitary stalk were exposed by a transpharyngeal approach. Cells recorded with glass micro‐electrodes from the ventral hypothalamus near the bifurcation of the internal carotid artery were identified as supraoptic neurones only when their antidromic action potential evoked at constant latency by stimulation of the pituitary stalk was cancelled by collision with a spontaneously occurring action potential.

2. More than 80% of the identified cells were spontaneously active. The frequency of firing was often slow (under 1 Hz) and rather irregular. More than half the cells, however, had a more distinctive firing pattern which recurred every 1‐3 min and consisted of a period of low or absent activity alternating with periods of quite marked discharge which occasionally exceeded 20 Hz. This periodicity was retained when the over‐all activity was enhanced by an intracarotid injection of 0·2 ml. 5% (w/v) NaCl.

3. Of fifty‐two cells tested, thirty‐six were excited by acetylcholine applied by iontophoresis from a multibarrelled micropipette with average ejection currents of 35 ± 5 nA (
S.D. of thirty‐six observations). Ten of these cells were also excited by nicotine applied with similar currents.
Compensatory hypertrophy of the contralateral kidney after unilateral ureteral ligation
Authors: Dicker S. E. , Shirley D. G.
Published: December 2014

1. The ligation of one ureter is accompanied by compensatory hypertrophy of the contralateral kidney.

2. The rate of growth of the contralateral kidney after ligation of the opposite ureter is similar to that observed after unilateral nephrectomy.

3. Ligation of one ureter produced ipsilateral hydronephrosis.

4. The development of hydronephrosis was accompanied by a marked increase of DNA, suggesting hyperplasia, and of the rate of anaerobic glycolysis, while the rate of oxygen uptake decreased, especially in the cortex.

5. During compensatory hypertrophy of the contralateral kidney, after ligation of the opposite ureter, there were increases of RNA/DNA ratios and of oxygen uptake, especially marked in the cortex, and in every respect similar to those observed after unilateral nephrectomy.

6. Ligation of one ureter resulted in an increase of glomerular filtration rate of the contralateral kidney similar to that observed after unilateral nephrectomy.

7. The mechanisms of contralateral renal hypertrophy after ligation of one ureter and after unilateral nephrectomy are discussed. It is suggested that in both cases the prime mover to compensatory hypertrophy is the increase of glomerular filtration rate.
The effect of angiotensin, noradrenaline and vasopressin on blood flow distribution in the rat kidney
Authors: Finberg J. P. M. , Peart W. S.
Published: December 2014

1. The effect of val5‐angiotensin II amide, noradrenaline and vasopressin, on kidney volume and intrarenal distribution of carbon particles and thioflavine S was examined in the rat.

2. Angiotensin produced a dose‐dependent shrinkage of the kidney coinciding with the rise in systemic blood pressure. Noradrenaline and vasopressin, however, produced reduction in kidney volume only in much higher doses than were necessary to produce a pressor effect.

3. An intravenous infusion of angiotensin sufficient to produce a diuretic response resulted in a striking increase in glomerular content of injected carbon particles, and a marked reduction in filling of the capillary plexuses of the subcortex and outer medulla. The reduction in outer medullary filling was also observed using the thioflavine S technique.

4. Noradrenaline infused in amounts sufficient to produce diuresis, aortic constriction above the kidney and vasopressin injection produced no measurable change in carbon particle distribution.

5. The reduction in capillary blood flow produced by angiotensin may result in impaired tubular reabsorptive capacity by reducing peritubular removal of reabsorbate, or by reducing oxygen availability. Thus the vasoconstrictor effects of angiotensin may explain its diuretic action.
Pharmacological properties, cholinesterase activity and anatomy of nerve—muscle junctions in vagus‐innervated frog sartorius
Authors: Landmesser Lynn
Published: December 2014

1. The pharmacological properties of the nerve—muscle junctions of vagus‐innervated frog sartorius muscles were investigated. Vagus‐evoked junctional potentials were ten times more sensitive to hexamethonium than were control end‐plate potentials from muscles re‐innervated with sartorius nerve. Hexamethonium did not affect passive electrical muscle membrane properties or quantal content. The sensitivity of vagus junctions to
D‐tubocurarine (dTC) did not differ from the controls.

2. The amplitude and time course of vagus‐evoked junctional potentials were not affected by eserine or neostigmine. Furthermore, histologically detectable acetylcholinesterase activity was not demonstrable at vagus‐muscle junctions.

3. The ultrastructure of vagus‐innervated muscle fibres was normal in appearance indicating that the vagus was capable of structurally maintaining the muscle fibres.

4. Junctional contacts were made by varicosities of unmyelinated vagal fibres. Although such varicose vagal fibres ran along the muscle fibres for long distances, they seemed to make synaptic contacts primarily at old end‐plate regions, as deduced from persisting junctional folds.

5. It is concluded that at least several ‘trophic’ factors are probably involved in the different effects of the vagus nerve on the sartorius muscle.
Ionic differences between somatic and axonal action potentials in snail giant neurones
Authors: Wald Flora
Published: December 2014

1. The ionic requirements of the somatic and axonal action potentials of ‘H’ neurones of the snail Cryptomphallus aspersa were studied using intracellular micro‐electrodes.

2. The overshoot of the somatic action potential increased by 10 mV for a tenfold increase in [Ca2+]o. In calcium‐free media the action potential decreased gradually to values of 50 to 90% of the control and they could be completely eliminated with 2 m
M‐EGTA. The maximum rate of rise also varied with [Ca2+]o.

3. After 2 hr in sodium‐free solution the somatic action potential decreased 6% in overshoot and 24% in rate of rise.

4. The somatic action potential was not affected by TTX, 5 × 10−6 g/ml. Procaine, 18 m
M, reduced its rate of rise but did not eliminate it whereas 30 m
M‐CoCl2 did.

5. The size of the axonal action potential increased with increased [Na+]o, but decreased with an increase in [Ca2+]o.

6. Procaine, 18 m
M, abolished the axonal action potential whereas it was not affected by TTX, 5 × 10−6 g/ml., nor, usually, by 30 m
M‐CoCl2.

7. The results obtained by studying the compound action potential of the nerves were similar to those from axonal action potentials.

8. The possibility that the somatic action potential is mainly calcium dependent while the axonal action potential is mainly produced by sodium is discussed.
The sensitivity of the hepatic glycogenolytic mechanism to stimulation of the splanchnic nerves
Authors: Edwards A. V.
Published: December 2014

1. The sensitivity of the hepatic glycogenolytic mechanism to splanchnic nerve stimulation at relatively low frequencies has been investigated in adrenalectomized calves, dogs and cats.

2. In young calves the hyperglycaemic response to splanchnic nerve stimulation at 1·0 c/s for 5 min increased steadily during the first 2 weeks after birth.

3. The hyperglycaemic response to splanchnic nerve stimulation for 5 min was directly related to frequency of stimulation within the range 0·5–4·0 c/s in calves tested 2‐5 weeks after birth. Pronounced rises in plasma glucose concentration also occurred in calves of this age in response to maximal stimulation (20 c/s) for shorter periods (30 sec) whereas occlusion of the portal vein for the same period produced no comparable effect.

4. The effects of splanchnic nerve stimulation for prolonged periods were also investigated in 2‐ to 5‐week‐old calves. Under these conditions increased concentrations of glucose in the plasma were maintained for periods of up to 90 min and fell towards the initial values when stimulation was discontinued.

5. Prolonged stimulation of the peripheral ends of both splanchnic nerves at either 2·0 or 4·0 c/s produced a transient reversal of hypoglycaemia in calves pretreated with large doses of insulin; both the extent and duration of these responses were related to frequency of stimulation.

6. The hyperglycaemic response to bilateral splanchnic nerve stimulation was directly related to frequency of stimulation within the range 0·5–4·0 c/s in adrenalectomized dogs. Comparable responses were obtained in adrenalectomized cats in response to stimulation at 2·0 c/s, but stimulation at 1·0 c/s produced no rise in mean plasma glucose concentration in these animals.

7. The sensitivity of the hepatic glycogenolytic mechanism has been assessed in relation to the associated changes in haematocrit and mean aortic blood pressure under the same conditions.

8. The results of these experiments support the contention that tonic changes in sympathetic efferent activity are associated with variations in the rate at which glucose is released from the liver under physiological conditions.
Image quality of the cat eye measured during retinal ganglion cell experiments
Authors: Bonds A. B. , Enroth-Cugell Christina , Pinto L. H.
Published: December 2014

1. The modulation transfer function (MTF) of the dioptrics of fifteen cat eyes was determined. The aerial image, formed by the eye of a standard object (a 0·5–1·0° annulus), was photographed. The transmission of the film negative was measured with a scanning microdensitometer to yield the light distribution within the aerial image. Correcting for the double passage, this experimentally determined light distribution and the known object light distribution were used to obtain the MTF, applying Fourier methods. Each MTF was used to calculate the light distribution within the retinal image of stimuli of various geometry used in experiments on retinal ganglion cells in the same eye.

2. When the eye was equipped with an artificial pupil of the same size as that used in the neurophysiological experiments (4·0–4·8 mm diam.) the MTF had fallen to 0·5 at 2·43 c/deg. When the pupil was removed the MTF had fallen to 0·5 at a much lower spatial frequency (1·0 c/deg). This shows that even when one uses an artificial pupil too large to provide optimal image quality there is a vast improvement over using no pupil.

3. These image quality measurements were prompted by the need to know the actual stimulus image in experiments on the functional organization of the receptive field, a need exemplified in this paper by a few specific physiological results. The full neurophysiological results appear in the next two papers.
Properties of the surround response mechanism of cat retinal ganglion cells and centre‐surround interaction
Authors: Enroth-Cugell Christina , Pinto L. H.
Published: December 2014

1. The properties of the surround response mechanism of on‐centre cells and its interaction with the centre mechanism were studied by recording from single optic tract fibres. In many of the experiments the spatial distribution of the light within the retinal image of the stimuli was measured.

2. Pure surround responses of on‐centre cells were isolated using a centrally located steady light which selectively desensitized (adapted) the centre mechanism. This permitted a peripheral flashing stimulus whose luminance varied over a range as great as 1·38 log units to elicit surround responses which, for any given cell, were of invariant shape. The rate of decay of the firing frequency of the spike burst at ‘off’ varied from cell to cell. The general characteristics of such pure surround responses to squarewave stimuli were described. The plot of the magnitude of pure responses against stimulus luminance, at constant background conditions, was curvilinear.

3. The pure surround response of two off‐centre cells was isolated; it was similar in shape to the pure centre response of on‐centre cells.

4. Interaction of centre and surround mechanisms of on‐centre cells was studied by eliciting a pure central and a pure surround response from the same cell. The electronically obtained algebraic sum of these two pure responses equalled the mixed response of the ganglion cell to simultaneous presentation of the stimuli which evoked the pure responses when presented singly. This is probably best explained by algebraic summation of centre and surround inputs.

5. The pure surround response from two cells to a fixed flashing stimulus was attenuated by a steady field adapting light, both when this was superimposed upon the stimulus and when not superimposed. In the latter case, (i) when the spatial separation between the flashing stimulus and the adapting light was at a minimum, less than 10% of the adapting flux fell inside the boundaries of the stimulating flux, and (ii) the response was attenuated also if the adapting light was in the geometric centre of the receptive field. These results indicate that the adaptation pool of the surround mechanism extends to the central portions of the receptive field.

6. Nearly half the cells tested did not yield pure surround responses. This was probably due to differences, within the ganglion cell population, (i) of the spatial distribution of the ratio of centre to surround signal sensitivity and (ii) of differences in the ratio of centre to surround adaptivity in the receptive field middle. It was not due to excess adaptive flux falling outside the region of maximal centre mechanism adaptivity, nor due to excess stimulus flux falling inside the region of maximal signal sensitivity.
Activation of the electrogenic sodium pump in guinea‐pig auricles by internal sodium ions
Authors: Glitsch H. G.
Published: December 2014

1. The effect of various intracellular Na concentrations ([Na]i) on the membrane potential after hypothermia was studied in guinea‐pig auricles.

2. For varying [Na]i, the atria were cooled for 4 hr at 4‐6° C in a K‐poor solution with different concentrations of NaCl. The auricles were rewarmed in normal Tyrode solution at 35° C.

3. Extracellular space (ECS), intracellular Na and K concentrations ([Na]i and [K]i) and membrane potential of the atria were measured before and after hypothermia.

4. The ECS, measured as inulin space, amounted to 350 ml./kg wet wt. at 35° C and to 300 ml./kg wet wt. at 4‐6° C.

5. [K]i decreased during cooling and increased during rewarming the auricles. [Na]i increased during hypothermia in bathing fluids containing NaCl, but decreased in NaCl‐ and Na‐free solutions. At the beginning of rewarming a net Na transport occurred from cells with high [Na]i, while a net Na uptake took place in atria with low [Na]i.

6. At the same time, the membrane potential of auricles with increased [Na]i hyperpolarized beyond the steady‐state value recorded at the end of rewarming, or even beyond the calculated K+ equilibrium potential (EK). Afterwards, the hyperpolarization levelled off, while the EK values increased further. The membrane potential of atria with decreased [Na]i showed no transitory hyperpolarization during rewarming.

7. The hyperpolarization beyond the steady‐state value of membrane potential in rewarmed auricles was significantly correlated to the active Na efflux.

8. From these results it is concluded that the membrane potential of guinea‐pig atria after hypothermia is affected by an active, electrogenic Na pump activated by intracellular Na ions.
Energetics of activation in frog and toad muscle
Authors: Smith I. C. H.
Published: December 2014

1. If activation heat reflects the operation of the calcium pump it should be independent of actomyosin activity. The semitendinosus preparation affords a technique for removing actomyosin activity since the muscle can be stretched till there is almost no overlap between the filaments.

2. Heat production, H, in twitches and tetani of stretched muscle fits the relation H = A+M.P/Pot where P/Pot is the fraction of the optimal tension remaining at the stretched length and A and M are assumed to be the activation dependent and actomyosin dependent heat components.

3. For twitches the A component is early and fast and constitutes 0·26 (
S.D. 0·09) of the heat production at normal muscle lengths. Its time course is similar in both frog and toad muscle although both M and P are twofold slower in toad muscle. High concentrations of CO2 slow only M and Pot. The A component is associated with a normal recovery heat.

4. The twitch‐tetanus tension ratio, after correction for the extra shortening that occurs during a tetanus, does not vary with the degree of muscle stretch: it is thus probable that twitch activation does not vary with muscle stretch.

5. Moderately hypertonic Ringer solution reduces M and Pot but not A, but strongly hypertonic solution also reduces A. Zn2+, No3− and second shock potentiation of a twitch increase A, M and Pot in proportion to each other.
Effect of chemical sympathectomy on the content of acetylcholine, choline and choline acetyltransferase activity in the cat spleen and iris
Authors: Consolo S. , Garattini S. , Ladinsky H. , Thoenen H.
Published: December 2014

1. Acetylcholine and choline were measured in the spleens and irides of normal and 6‐hydroxydopamine‐treated cats. In addition, choline acetyltransferase activity was measured in the spleens.

2. No acetylcholine or choline acetyltransferase activity were found in spleens of normal or treated cats. The choline content of normal spleens was 12·4 ± 1·5 μg/g wet wt. (mean ±
S.E. of mean), which was not significantly altered by chemical sympathectomy.

3. The acetylcholine and choline contents of the cat iris were 3·0 ± 0·3 μg/g wet wt. and 7·7 ± 0·9 μg/g wet wt., respectively. There was no difference in acetylcholine and choline concentrations between left and right or normal and sympathectomized irides.

4. These results are discussed in relation to the question of a cholinergic link in post‐ganglionic sympathetic transmission.
Relationships between blood flow and secretion in the isolated perfused canine pancreas
Authors: Augier Danièle , Boucard J. P. , Pascal J. P. , Ribet A. , Vaysse Nicole
Published: December 2014

1. Stimulation by a continuous intra‐arterial infusion of secretin caused a marked vasodilatation in the pancreato‐duodenal preparation or in the isolated pancreas perfused with whole heparinized blood. There was no difference in the vasomotor effects of two unequally purified preparations of secretin. The fact that the vasodilatation was still observed when the duodenum was removed proved that the haemodynamic effect of secretin was initiated in the pancreas itself.

2. The secretory response of the pancreas to a given dose of secretin was larger when the blood pressure was kept constant by increasing the blood flow than when the blood pressure was allowed to fall by maintaining the blood flow at a fixed value. It is concluded that the vasodilatation plays a role in the functional regulation of the pancreatic response to secretin.

3. The correlation between blood flow and arterial pressure on the one hand, and the secretory response to secretin on the other, was not mediated by the control of respiration since there was no variation in oxygen uptake in response to a variation in the blood flow. This correlation was still observed when the venous blood was discarded and therefore could not be explained by variations in the rate of recirculation of secretin. It was observed too in experiments where the duodenum was removed, the pancreas alone being introduced into the perfusion apparatus, which indicated that this effect was not mediated by a control of the release of secretin by the duodenum.
The effect of diameter on the electrical constants of frog skeletal muscle fibres
Authors: Hodgkin A. L. , Nakajima S.
Published: December 2014

1. Electrical constants were determined on isolated single fibres or on fibres from bundles from frog's twitch muscles by analysing the low frequency cable properties.

2. The sarcoplasmic conductivity (Gi) was 5·9 mmho/cm at 20° C, and its temperature coefficient (Q10) was 1·37.

3. The Q10 of the membrane conductance (GM) was 1·49, and that of the membrane capacity (CM) was 1·02.

4. CM increases with diameter (D) in an approximately linear manner: the values were 4·6 μF/cm2 at D = 50 μ, and 8·5 μF/cm2 at D = 130 μ.

5. GM also increases with diameter, being 0·21 mmho/cm2 at D = 50 μ and 0·37 mmho/cm2 at D = 130 μ.

6. These results suggest that the transverse tubular system contributes substantially to the values of low frequency capacity and conductance measured at the surface membrane.
Proximal negative response in the pigeon retina
Authors: Holden A. L.
Published: December 2014

1. The proximal negative response (PNR) of the inner plexiform layer of the pigeon retina was recorded intraretinally.

2. The PNR can be distinguished from the local b‐wave by its area dependence, and its depth profile in the retina.

3. The ‘on’ and ‘off’ transients of the PNR have differing depth profiles in the retina: the ‘on’ transient is distributed vitreal to the ‘off’, and both are distributed vitreal to the b‐wave.

4. As spot diameter is increased, so the amplitude of the PNR decreases, and the threshold rises.

5. Ganglion cells fire at ‘on’ and ‘off’ during the PNR and like the PNR, are suppressed as spot size is increased.
A study of frog muscle maintained in organ culture
Authors: Harris A. J. , Miledi R.
Published: December 2014

1. Frog muscles are isolated and maintained in organ culture conditions for periods of up to 2 months. During the first 2 weeks, muscle fibres have normal resting membrane and action potentials. Subsequently the potentials decline in amplitude.

2. Slow muscle fibres also survive in culture and retain their ability to give maintained contractures.

3. Muscle sensory receptors continue to function in culture until the axon terminals degenerate at about 2 weeks.

4. Neuromuscular transmission is normal during the first few days of culture, after which the motor endings degenerate. Transmission persists longer (up to 17 days) if a long segment of nerve is left attached to the muscle. With short‐nerve preparations failure of transmission in vivo occurs at about the same time as in culture. With long‐nerve preparations failure of transmission is delayed even further in culture.

5. In short‐nerve preparations miniature end‐plate potentials disappear, in general, at about the time that transmission fails. In long‐nerve preparations some end‐plates continue to have miniature end‐plate potential activity for a short time after nerve impulses cease to evoke any response; but eventually miniature potential activity disappears from all end‐plates.

6. After a few days of electrical silence, miniature end‐plate potentials reappear at some of the denervated end‐plates. The proportion of denervated end‐plates which show miniature end‐plate potentials in culture is smaller than in muscles denervated in situ.

7. Electron microscopy shows that muscle structure is well preserved in culture, that the axons degenerate and that the Schwann cells move to occupy the space vacated by the axons. The Schwann cells are very probably the source of the acetylcholine which evokes miniature potentials in the denervated end‐plates.
The transport of L‐leucine in human erythrocytes: a new kinetic analysis
Authors: Hoare D. G.
Published: December 2014

1. Data on the transport of
L‐leucine into human erythrocytes at 25° C shows (a) that the carrier re‐orientation process is rate determining, (b) that the binding of leucine to the carrier increases the rate of carrier re‐orientation and (c) that the carrier is, at equilibrium, about equally distributed between the membrane surfaces at 25° C.

2. These conclusions are reached through a new kinetic analysis of a simple carrier system, which involves no prior assumptions about the relative magnitudes of the rate constants, yet leads to usable kinetic equations. These equations allow the determination of the rate determining step, the calculation of the effect of bound substrate on the rate of carrier re‐orientation and, in some cases, an estimate to be made of the equilibrium distribution of the carrier between the inner and outer membrane surfaces.
The temperature dependence of the transport of L‐leucine in human erythrocytes
Authors: Hoare D. G.
Published: December 2014

1. Experiments are reported on the entry, exit and exchange fluxes of
L‐leucine in human erythrocytes in the temperature range 0–37° C. The kinetics of entry and exit become quite different at low temperatures, indicating an asymmetry in the transport mechanism.

2. The data is analysed in terms of a simple carrier mechanism. This shows that carrier re‐orientation is rate determining at all temperatures studied, and suggests, although does not prove, that the origin of the asymmetry of the carrier may be an unequal equilibrium distribution of the carriers between inward and outward orientations.

3. The activation energy increases sharply on going to low temperatures. This increase is the sum of two components. One arises from differences between the activation energies for inward and outward carrier re‐orientations, and the other from changes, with temperature, in the activation energies of the individual carrier re‐orientation steps.
Accumulation and apparent active transport of prostaglandins by some rabbit tissues in vitro
Authors: Bito L. Z.
Published: December 2014

1. Slices or bits of rabbit tissues, not exceeding 100 mg, were incubated in tissue culture medium containing tritium‐labelled prostaglandin ([3H]PG). In some experiments, incubation medium also contained saturating concentrations of an unlabelled prostaglandin (PG), or [14C]‐sucrose for determination of extracellular space. At the end of the incubation period, usually 1 hr, the tissues were removed and weighed, and their 3H (and 14C) content were determined along with that of a unit volume of medium.

2. Tissues known to play a central role in PG metabolism (lung and liver) and in its excretion (kidney cortex) and tissues which have a known function in blood‐brain and blood‐ocular barriers (choroid plexuses and ciliary processes) show a large accumulation of 3H when incubated in a medium containing [3H]PGE1. In addition, tissues of the female reproductive tract, and the aorta of the rabbit show similar 3H accumulation. When uncorrected for tissue solid content or extracellular water volume, the extent of this accumulation is two‐ to sixfold. Calculated on the basis that all excess 3H is present in the free form in the intracellular water, the accumulation ratio for ciliary processes, for example, indicates an over fortysix‐fold gradient of PGE1 across the cell membrane.

3. Tissues which accumulate [3H]PGE1 also accumulate [3H]PGA1, [3H]PGF1α and [3H]PGF2α. In some tissues specificity is, however, apparent; in the lung accumulation of [3H]PGA1 was significantly greater than that of [3H]PGF1α.

4. The extent of [3H]PGE1 accumulation was decreased, or in some tissues completely inhibited, by incubation at 2° C, or by addition of large concentrations of unlabelled PG.

5. Accumulation of [3H]PGE1 by the foetal liver is not apparent on the 20th day of gestation, but is fully developed by the 30th day of gestation. The foetal lung does not accumulate [3H]PGE1 at any stage of gestation.

6. In some tissues, most notably muscle, there appears to be full equilibrium of [3H]PGE1 between tissue water and medium within 1 hr of incubation.

7. PGs are partially excluded from the intracellular volume of some other tissues, most notably the spleen and subcutaneous connective tissues. This apparent exclusion cannot be blocked by incubation in the cold, or by the addition of saturating levels of unlabelled PG.

8. The simplest explanation for all observed results is that cell membranes are, in general, impermeable to PGs. However, there are specific, carrier‐mediated mechanisms across some membranes which facilitate the entry of PGs. In some cells these transport mechanisms are linked to a source of metabolic energy, and/or to the counter‐transport of some other substance, thus allowing net accumulation of PGs against a concentration gradient. Alternatively, 3H accumulation may represent adsorption of [3H]PGs or one of their labelled metabolites on to specific adsorption sites.
An investigation of sodium transport in barnacle muscle fibres by means of the microsyringe technique
Authors: Bittar E. Edward , Chen Stephen , Danielson Bo G. , Hartmann Henrik A. , Tong Edmund Y.
Published: December 2014

1. The cation composition of single barnacle muscle fibres following damage by axial insertion of a microsyringe has been measured. The Na and Ca contents of these fibres were raised.

2. Electronmicroscopic studies of fibres following insertion of a microsyringe indicated that the damage done resulted in tubular obstruction of the T‐system.

3. Fibres loaded with radiosodium by micro‐injection showed that the Na* efflux declined exponentially with time, but that in most fibres the slope ratio of d/dt ln [Na*]1 to d/dt (ln d[Na*]i/dt) was less than unity. Injections of distilled water deep in the fibre failed to influence the course of the Na* efflux.

4. K removal reduced the Na efflux by 47%. However, a few fibres displayed very little K‐dependence.

5. When measured in fibres already soaked in a K‐free medium for long periods the sodium efflux consisted of a brief rapid phase, followed by a slow phase of Na loss.

6. In the presence of 30 m
M‐K, there was little or no rise in the Na efflux. Raising the external K to 50 or 100 m
M caused a marked rise in the Na efflux. Raising the external K to 30 m
M in the absence of external Ca2+ led to a rise in the Na efflux. A high K solution always caused shortening of these fibres.

7. Internal application of 1
M or 1 m
M‐CaCl2 often caused a significant rise in the Na efflux.

8. Internal application of 2·5 or 5
M saline caused a prompt and large fall in the Na efflux. In the presence of high K saline‐loaded fibres failed to contract.

9. Internal application of 0·5
M‐ATP stimulated the Na efflux. A larger effect was not observed in fibres pre‐treated with 2
M‐MgCl2. Internal application of 0·5
M‐ArP was without effect.

10. The results indicate that the barnacle fibre is a suitable preparation for the study of Na fluxes by means of the micro‐injection technique. They also indicate that the mechanism regulating the Na efflux is not quite the same as that found in squid axon or frog muscle.
Some properties of the presynaptic nerve terminals in a mammalian sympathetic ganglion
Authors: Dunant Y.
Published: December 2014

1. Superior cervical ganglia of adult rats were excised and maintained in vitro in stable conditions. Potentials were recorded with external electrodes. After transmission was blocked by mecamylamine, a small potential change was recorded from the rostral area of the ganglion in response to preganglionic stimulation.

2. This electrical response was identified as the presynaptic action potential recorded from the nerve terminals by a number of criteria based on histological and physiological considerations including the disappearance of the spike in a glucose free solution. As shown by Nicolescu, Dolivo, Rouiller & Foroglou‐Kerameus (1966) on the same preparation this condition causes an irreversible and selective lesion of the presynaptic nerve endings.

3. A suitable concentration of mecamylamine permitted the presynaptic response and the excitatory post‐synaptic potential (EPSP) to be recorded simultaneously. As the stimulus was increased, the EPSP increased linearly with the amplitude of the presynaptic response.

4. After replacement of potassium ions in the bathing solution by caesium and during the early phase of post‐tetanic facilitation there was an increase in the presynaptic response accompanied by a disproportionate increase in the EPSP.

5. No changes in the presynaptic response were found in the presence of the following drugs, all of which depressed the EPSP: acetylcholine, hemicholinium, curare, further doses of ganglion‐blocking agents, and high Mg2+ and low Ca2+ concentrations.

6. Ouabain (4·5 × 10−4
M) reversibly decreased the amplitude of the presynaptic response and increased the spontaneous release of transmitter. The EPSP was at first enhanced and then depressed.