bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes of of extracellular potassium concentration induced by neuronal activity in the spinal cord of the cat
Authors: Kříž N. , Syková Eva , Ujec E. , Vyklický L.
Published: December 2014

1. Changes of extracellular K+ concentration, [K]e, arising in the spinal cord of the cat in response to an afferent stimulation were studied by means of K+‐specific micro‐electrodes.

2. In the most active areas of the spinal cord a single volley in a large afferent input like the common peroneal nerve or the posterior tibial nerve produced a transient increase in [K]e of 0·05–0·1 m
M, which reached its peak in 0·2–0·3 sec and it declined in about 3 sec.

3. Much higher increases in [K]e were found during repetitive stimulation of an afferent input. The highest increase (by 3 m
M) was at 100 Hz, but even at 1 Hz a significant increase of 0·25 m
M was observed. Equilibration of accumulated K+ was slow with a time constant of about 6 sec, which is much longer than could be expected for the same process in free solution.

4. A characteristic distribution of increased [K]e was found in the spinal cord in response to 100 Hz afferent stimulation. The highest increase of 3 m
M was found in and around the intermediate nucleus, but at depths between 0·9–1·8 mm the [K]e increase exceeded 1 m
M.

5. In the ventral horns afferent stimulation (100 Hz) increased [K]e by 0·25 m
M, while the same stimulation of the ventral root resulted in a [K]e increase of less than 0·05 m
M.

6. The consequences of Ke+ accumulation after neuronal discharge are discussed in respect to its possible role in the depolarization of primary afferent terminals.
A nervous mechanism for descending inhibition in guinea‐pig small intestine
Authors: Hirst G. D. S. , McKirdy H. C.
Published: December 2014

1. Intracellular recordings were made from neurones in the myenteric plexus of guinea‐pig small intestine under conditions in which these neurones received synaptic input from an adjacent segment of intestine.

2. Most long synaptic pathways in the myenteric plexus were found to lead in an anal direction.

3. Such pathways could be excited by either distension or transmural electrical stimulation of the intestinal segment.

4. Similar stimuli evoked inhibitory junction potentials in the circular muscle layer but only on the anal side of the stimulated region of intestine.

5. The results are discussed in relation to the concept of descending inhibition (Bayliss & Starling, 1899).
The regulation of cellular volume in liver slices
Authors: Macknight A. D. C. , Pilgrim Jennifer P. , Robinson Bridget A.
Published: December 2014

1. Rat, rabbit and guinea‐pig liver slices were incubated in media at 37° C to study effects of ouabain and of metabolic inhibition on tissue composition.

2. Slices initially incubated in oxygenated balanced medium did not swell when exposed to either balanced media or potassium‐free media containing ouabain in concentrations ranging from 0·1 to 10 m
M though they lost potassium and gained a comparable amount of sodium.

3. Without prior incubation in oxygenated medium slices initially swelled when incubated with ouabain but then maintained their new volume.

4. Slices whose metabolism was inhibited by incubation with nitrogen and 1 or 10 m
M iodoacetamide lost as much potassium as slices exposed to 10 m
M ouabain but became swollen with the uptake of sodium, chloride and water.

5. The results show that liver cells, like renal cortical cells, possess a metabolically dependent, ouabain‐insensitive, potassium‐independent mechanism concerned in the regulation of cellular volume.
The cyclic motility of the omasum and its control in sheep
Authors: Bueno L. , Ruckebusch Y.
Published: December 2014

1. The mechanical activity of different parts of the omasum was recorded by means of small balloons and/or strain‐gauges in conscious sheep. These events were related to the electrical activity of the omasal body, the omasal groove and the leaves and to the changes in diameter of the reticulo‐omasal orifice. Humoral, behavioural and nervous influences were examined.

2. Two patterns of contraction of the omasum were found. One, confined to the oral and middle thirds of the organ, originated at the omasal groove and proceeded to the right and then the left surfaces of the body and ceased at the onset of reticular contraction. The other was limited to the aboral third of the organ near the abomasum; in this part the contractions were prolonged regardless of the reticular contraction and some gave rise to a reversed propagation over the organ. The characteristic cyclic motility of the omasum was slightly reduced in sheep fasted for 48 hr and in those fed on pelleted food, and it persisted after vagotomy.

3. The reticulo‐omasal orifice always dilated strongly during the second phase of reticular contraction. It also dilated noticeably during the extra‐contraction associated with regurgitation. In each case alternating opening and closing movements at a frequency of 5–7/min followed. Contractions of the omasal leaves, which were independent of those of the omasal body, occurred at a rate of approximately 2–3/min. They passed from the free border to the base and travelled in an aboral direction. After local application of fatty acids the frequency of their contractions increased to approximately the same rate as that of the orifice.

4. It is concluded that the motility of the omasum in sheep involves a wave of contraction starting at a point on the omasal groove just posterior to the reticulo‐omasal orifice and passing slowly over the omasal body. With the exception of the occasional reversed contractions this pattern is closely associated with rumino‐reticular cycles even though the omasal contractions and the movements of the leaves are partially independent of vagal innervation.
Effects of rapid cooling on the electrical properties of the smooth muscle of the guinea‐pig urinary bladder
Authors: Kurihara S. , Kuriyama H. , Magaribuchi T.
Published: December 2014

The effects of low temperature (36–10° C) on the electrical properties of smooth muscle cells of the urinary bladder were investigated with microelectrodes and the double sucrose gap method.

1. Lowering the temperature from 36 to 20 and to 10° C, depolarized the membrane from −37 to −33 and to −25 mV respectively. Spontaneous and propagated spike activity ceased completely at below 20° C but evoked spikes were occasionally observed at 10° C. A sustained contracture was evoked below 25° C.

2. At both normal and low temperatures, the tissue had cable‐like properties. The length constant was reduced from 1·82 mm (36° C) to 1·54 mm (20° C) and to 1·04 mm (10° C). On the other hand, the time constant of the membrane calculated from the cable equations was prolonged by lowering the temperature from 157 msec (36° C) to 257 msec (20° C) and to 508 msec (10° C). The effective resistance of the membrane was increased to 1·8 times at 20° C and to 2·9 times the control value at 10° C.

3. From the changes in various parameters of the membrane at low temperature, an increase in the longitudinal resistance of the tissue was postulated.

4. The possible mechanisms of action of low temperature on the electrical properties of the smooth muscle of the urinary bladder were discussed in relation to those of the taenia coli and stomach, especially on the effects of low temperature on the sequestered Ca in the cell.
Light and X‐ray diffraction studies on chick skeletal muscle under controlled physiological conditions
Authors: Matsubara Ichiro
Published: December 2014

1. The sarcomere length (s) of ehick slow and fast muscles (anterior and posterior latissimus dorsi (ant. lat. dorsi and post. lat. dorsi)) was measured by the method of light diffraction. In resting ant. lat. dorsi, s changed from 1·76 to 2·30 μm during stretch from minimum to maximum muscle lengths in situ, and in resting post. lat. dorsi from 2·18 to 2·63 μm.

2. Resting tension started to rise in ant. lat. dorsi when s exceeded 1·7–1·8 μm, but in post. lat. dorsi not until s exceeded 2·6–2·7 μm.

3. X‐ray diffraction patterns showed that ant. lat. dorsi contains collagen filaments; collagen reflexions were not seen in patterns obtained from post. lat. dorsi with the same exposure time.

4. The relation between active tension and sarcomere length was similar for ant. and post. lat. dorsi. The maximum active tension was observed when s = 2·05–2·15 μm in ant. lat. dorsi, and when s = 2·10–2·25 μm in post. lat. dorsi.

5. X‐ray diffraction patterns from both muscles showed that the periodic structures of the thick and thin filaments are similar to those in frog and rabbit skeletal muscles.

6. The volume of the myofilament lattice in resting ant. lat. dorsi was 3·06 (± 0·14) × 109 Å3, in resting post. lat. dorsi 2·98 (± 0·09) × 109 Å3. These values are close to that of frog skeletal muscle. The lattice volume remained constant in ant. lat. dorsi and post. lat. dorsi over the range of sarcomere lengths found in situ.

7. The equatorial diffraction patterns from the ant. lat. dorsi in rigor (glycerol extracted) were different from that of the resting muscle, and suggested that a large number of cross‐bridges were attached to the thin filaments during rigor. During potassium contracture, however, the diffraction pattern remained similar to that from the resting ant. lat. dorsi.
The autonomic innervation of the nasal blood vessels of the cat
Authors: Eccles R. , Wilson H.
Published: December 2014

1. A study has been made in the anaesthetized cat of the stimulation parameters required to separate the vasodilator and vasoconstrictor responses evoked in the nose by stimulating the cut peripheral end of the Vidian nerve.

2. The extent of the vasodilation and vasoconstriction was found to be dependent on the stimulation frequency, but whereas vasodilation reached a maximum at 25 Hz, vasoconstriction occurred at lower frequencies and was maximum between 10 and 15 Hz.

3. Atropine, in a dose much greater than that which inhibits nasal secretion, did not abolish the vasodilator responses evoked by Vidian nerve stimulation. This suggests that the Vidian nerve may convey atropine resistant fibres to the nasal vasculature.
Work‐induced hypertrophy in exercised normal muscles of different ages and the reversibility of hypertrophy after cessation of exercise
Authors: Goldspink G. , Howells K. F.
Published: December 2014

1. Groups of male hamsters of different ages were subjected to a weight‐lifting exercise regimen, and the biceps brachii, soleus and extensor digitorum longus (EDL) muscles examined for structural changes occurring in response to the increased workload. In addition, two groups of adult hamsters were left to recover from the exercise stimulus for 5 and 15 weeks respectively.

2. All the exercised muscles exhibited muscle fibre hypertrophy, and the extent of the hypertrophy was greater in the younger animals. In all age groups, the biceps brachii and EDL showed more hypertrophy than did the soleus. There was no significant increase in fibre number after exercise.

3. In both groups allowed to recover from the exercise stimulus, the fibre dimensions reverted back to those of the control muscles; this appeared to be complete after 15 weeks recovery.

4. Electron microscopical studies of fibres from exercised and control biceps brachii revealed no significant changes with exercise in the proportions present of myofibrillar, mitochondrial and tubular components within muscle fibres of the same size.
Vacuolar transcellular channels as a drainage pathway for cerebrospinal fluid
Authors: Tripathi Brenda J. , Tripathi R. C.
Published: December 2014

1. Based on our ultrastructural investigations in monkeys, we report here a new concept as to the physiological mechanism of drainage of cerebrospinal fluid (c.s.f.) which would seem to bridge the gap between the two apparently opposing views of ‘closed’ and ‘open’ system.

2. Our studies reveal the presence of an intact mesothelial lining of the arachnoid mater, including its villus‐like projections and herniations into the dural sinus and its lacunae, adjacent cells being joined by tight junctions; in addition we have observed for the first time that many lining cells in the region of the superior sagittal sinus are characterized by unit membrane‐bound, electron‐optically empty giant vacuoles of several micrometres diameter. In one monkey with a fresh subarachnoid haemorrhage, many vacuoles were filled with plasma proteins and some contained intact blood corpuscles.

3. Serial section analysis showed that the vacuoles were in fact invaginations from the basal aspect of the cell surface and were evidently in direct communication with the c.s.f. in the subarachnoid space. Some vacuoles in addition showed openings on their apical surface thus constituting transcellular channels or pores. Basal openings up to 3·5 μm and apical openings up to 2·3 μm were seen.

4. It is postulated that vacuoles are stages in the formation of a dynamic system of transcellular pores which allow the bulk outflow of c.s.f. down a pressure gradient, and that the mesothelial vacuolation cycle, in providing the requisite number of transcellular pores across the mesothelial barrier at any time, is a controlling factor in the outflow of c.s.f. and in the maintenance of its fluid‐pressure within the subarachnoid space.

5. The basic similarity between the bulk flow of the aqueous humour and c.s.f. from the anatomically closed cavities of the anterior chamber and the subarachnoid space, respectively, is underlined.

6. The present study provides further support for our hypothesis that the bulk outflow of fluid, via a dynamic system of transcellular pores formed by gradually enlarging membranous surface infoldings in a single cell, termed as giant vacuoles, is a fundamental biological process not hitherto described.
Membrane currents and activation of contraction in rat ventricular fibres
Authors: Léoty Claude
Published: December 2014

1. A double sucrose gap technique has been combined with an optical method of measuring the movement of the preparation and applied to rat ventricular trabeculae.

2. Experiments performed in normal McEwen and in depleted sodium solutions with and without tetrodotoxin, manganese or predepolarization suggest that the fast inward current is not as important as the slow inward current in determining the contractile strength. Furthermore, there is a marked similarity between potential dependence of the slow inward current and the contraction, particularly in sodium‐depleted fluids.

3. The appearance of a staircase response associated with a series of depolarizations, in normal McEwen, may mean that there is an intervention of a further, possibly intracellular, stage between inward current and contraction, as suggested by earlier experiments on frog as well as on mammalian heart.
Drinking and antidiuresis elicited by isoprenaline in the dog
Authors: Fitzsimons J. T. , Szczepańska‐Sadowska Ewa
Published: December 2014

1. Isoprenaline hydrochloride injected subcutaneously or infused intravenously caused drinking and simultaneous antidiuresis in the dog. The minimal effective dose was between 20 and 50 μg per dog.

2. Isoprenaline‐induced drinking was prevented by the β‐adrenergic antagonist propranolol and enhanced by the α‐antagonist phentolamine.

3. Ganglionic blockade with pentolinium or with hexamethonium did not interfere with the response.

4. A delay of 1 hr after injection of 100 μg isoprenaline, before drinking was permitted, did not significantly reduce the amount of water subsequently drunk. A preload of water approximately equal to the volume of water normally drunk caused a greater reduction in water intake in some dogs.

5. Isoprenaline caused an increase in heart rate and pulse pressure which lasted for between 1 and 3 hr according to dose. Central venous pressure fell, but mean arterial pressure was little altered. Haemodynamic changes preceded drinking by about 5 min.

6. Infusion of isoprenaline caused drinking in the bilaterally nephrectomized dog.

7. We conclude that isoprenaline is a potent stimulus to drinking in the dog and that the effect is not exclusively mediated by the renin‐angiotensin system.
Specific membrane properties of cat motoneurones
Authors: Barrett J. N. , Crill W. E.
Published: December 2014

1. Electrophysiological properties of cat motoneurones were measured using intracellular electrodes, after which Procion dye was injected iontophoretically into the neurone through the recording pipette.

2. Histological procedures were chosen to minimize changes in neuronal morphology. Reconstructed motoneurones had more dendritic branches and larger surface areas than the Golgi‐stained motoneurones of earlier reports.

3. The sum of the 3/2 power of the dendritic diameters (the dendritic trunk parameter; Rall, 1959) of the reconstructed motoneurones was found to decrease with distance from the soma. Thus, the dendritic tree is not satisfactorily approximated by a non‐tapering membrane cylinder.

4. A computational technique was developed to allow calculation of the specific resistance (Rm) of the membrane using the measured value of the input resistance of the motoneurone and a more detailed approximation of the dendritic tree. These calculations indicate that the average resting value of dendritic Rm is at least 1800 Ω cm2. The specific membrane capacity, calculated assuming uniform Rm, ranged between 2–3 μF/cm2.
Studies on laryngeal calibre during stimulation of peripheral and central chemoreceptors, pneumothorax and increased respiratory loads
Authors: Dixon M. , Szereda‐Przestaszewska Małgorzata , Widdicombe J. G. , Wise J. C. M.
Published: December 2014

1. The effects of asphyxia, hypoxia, hypercapnia, stimulation of peripheral chemoreceptors, pneumothorax and breathing through resistances have been investigated on laryngeal resistance to airflow in anaesthetized cats, with and without bilateral vagotomy below the origin of the recurrent laryngeal nerves.

2. Resistance to airflow of the innervated larynx was usually measured with the larynx isolated in situ with constant flow from the trachea to a pharyngeal opening, and expressed by the relationship between translaryngeal pressure and airflow.

3. Asphyxia, hypoxia and hypercapnia each stimulated breathing and decreased laryngeal resistance to airflow, in both the inspiratory and expiratory phases. After vagotomy the effect was reduced, abolished or (usually) reversed to a laryngeal constriction, especially in expiration.

4. Intra‐arterial injections of potassium cyanide (to stimulate carotid body chemoreceptors) caused a short apnoea or an augmented breath followed by hyperpnoea, concurrently with expiratory constrictions of the larynx. The responses were usually stronger after bilateral vagotomy.

5. Pneumothorax caused tachypnoea, inspiratory dilatations and expiratory constrictions of the larynx. The responses were abolished by vagotomy.

6. Imposition of respiratory resistances dilated the larynx, in inspiration and expiration, while complete closure of trachea caused expiratory constrictions of the larynx. These changes did not depend on intact vagal pathways.

7. The results are discussed in terms of nervous control of the larynx in the different conditions.
Desensitization in the process of histamine secretion induced by antigen and dextran
Authors: Foreman J. C. , Garland L. G.
Published: December 2014

1. Antigen challenge of sensitized rat peritoneal mast cells in the absence of calcium failed to release histamine. The release when calcium was added subsequently declined rapidly, this desensitization being almost complete in 4 min.

2. Phosphatidyl serine (10 μg/ml.) reduced the rate of desensitization so that decay of the response to added calcium was not complete after 16 min.

3. Exposing normal cells to dextran resulted in a slow rate of desensitization, the response to phosphatidyl serine added with calcium having decayed by only 27% within 10 min.

4. Phosphatidyl serine added with dextran prevented desensitization so that the response to subsequently added calcium did not decay even after an interval of 20 min.

5. Cells activated by dextran and calcium became rapidly desensitized as shown by decay of the response to added phosphatidyl serine which was almost complete by 5 min.

6. Histamine release by the calcium ionophore (A 23187) added to cells at intervals before the addition of calcium did not show significant decay.

7. Desensitization of the cells to antigen did not change their response to the ionophore.
The kinetics of pancreatic amylase secretion and its relationship to volume flow and electrical conductance in the anaesthetized cat
Authors: Greenwell J. R. , Scratcherd T.
Published: December 2014

1. Enzyme secretion in response to short duration vagal stimulation or to rapid
I.V. injections of cholecystokinin‐pancreozymin (CCK‐PZ) or gastrin or to intra‐arterial injections of acetylcholine is a function of the volume of juice secreted and not primarily a function of time.

2. The output of amylase in response to each stimulus occurred in a constant volume of approximately 15 drops (0·5 ml.) regardless of the rate of background secretin stimulated flow of water and electrolyte.

3. It is argued that because amylase secretion occurs in this constant volume, it is due to the rapid secretion of enzyme into the duct system from the acini, and subsequently the secretin stimulated secretion of water and bicarbonate washes the enzyme from the duct system.

4. When enzyme secretion is stimulated an increase in the electrical conductance (measured at 1·592 kHz) occurs across the tail of the pancreas. This increased conductance has two components. An early peak associated with the extrusion of enzyme from the acinar cell and a later peak which is probably due to vasodilatation.

5. Atropine was without effect on both enzyme secretion and the conductance record when the stimulant was CCK‐PZ.

Atropine blocked enzyme secretion and both peaks of the conductance record in response to stimulation by acetylcholine.

Atropine blocked enzyme secretion and abolished the early phase of the conductance record, on vagal stimulation. It was without effect on the later peak which probably indicates an atropine resistant vasodilation of the pancreatic vessels.

6. When the vagus is stimulated on a background of submaximal electrolyte secretion caused by the intravenous infusion of secretin, the volume rate of secretion and the rate of amylase secretion follow a similar time course. The maximal volume response occurred between 7 Hz and 15 Hz and the maximal amylase output per impulse was at 5 Hz.
The distribution in the rabbit of choline administered by injection or infusion
Authors: Gardiner J. E. , Gwee M. C. E.
Published: December 2014

1. The concentration of choline in plasma, erythrocytes, skeletal muscle, heart, lung, liver, small intestine and kidneys and the changes that follow the injection or infusion of choline have been measured in rabbits anaesthetized with pentobarbitone.

2. The concentration of choline in the plasma of arterial blood was 11·8 ± 0·6 n‐mole/ml. and in the erythrocytes 28·4 ± 1·3 n‐mole/ml. blood.

3. All tissues contained a higher concentration of free choline than did plasma. The values range from 19·1 ± 2·2 n‐mole/g in skeletal muscle to 500 ± 25 n‐mole/g in the kidney.

4. In order of their choline concentrations the tissues were intestine (duodenal end) > kidney > intestine (caecal end) > liver > lung > brain > heart > erythrocytes > (blood) > skeletal muscle > plasma, while in order of the contribution to the total body choline they were liver > intestine > skeletal muscle > (blood) > kidney > erythrocytes > lung > brain > plasma > heart. The total free choline determined by these analyses was between 30–40 μmole/kg body weight, about one third being present in the liver.

5. The choline content of the small intestine varied along its length. The lowest amount being present in the portion adjoining the caecum.

6. Within 1 min of the injection of choline 100 or 300 μmole/kg, 70–90% had left the circulation. The proportionate loss was higher after 100 μmole/kg than after 300 μmole/kg.

7. The loss following 300 μmole/kg was increased if that dose were preceded by a dose of 100 μmole/kg 40 min earlier; this suggests some additional disposal mechanism(s) had been activated by the first dose.

8. Three minutes after the injection of choline 300 μmole/kg, about 60% was present as free choline in the tissues studied. The order of the concentration increases was kidneys > liver > muscle > lung > small intestine (caecal end) > heart > intestine > small intestine (duodenal end) > brain.

9. Forty minutes after the injection of choline 300 μmole/kg, only 11% could be accounted for as free choline. Only the levels in the kidney, liver, muscle and lung were significantly above normal at this time.

10. Infusion of choline 0·8 μmole/kg. min or greater produced rises in plasma choline that corresponded to a clearance of 32 ml. plasma/kg. min.

11. After the infusion of 300 μmole/kg over a period of 1 hr, raised levels of choline were detected in all tissues assayed, but the amount found accounted for only 14% of the choline administered. The concentrations in the kidney, liver and lung were similar to those found 40 min after the injection of 300 μmole/kg.

12. There was no change in the concentration of choline in the erythrocytes after the injection of choline 100 or 300 μmole/kg, nor during the infusion of choline at the rate of 5 μmole/kg. min for 1 hr.

13. The plasma volume appeared to be affected by the injection of the large doses of choline; after choline 300 μmole/kg the plasma volume was reduced. No effect on the plasma volume was observed during the infusion of the same dose.
Structure and function in urinary bladder of foetal sheep
Authors: France Venetia M. , Stanier Margaret W. , Wooding F. B. P.
Published: December 2014

1. The structure and function of the epithelial lining of the urinary bladder of sheep foetuses was investigated by electron microscopic studies made in conjunction with a series of experiments in which the permeability of the bladder to sodium and water was measured in vitro. Measurements were made at gestational ages ranging from 50 to 141 days (term = 147 days) Osmolarity and electrolyte concentrations of urine found in the foetal bladder were also measured.

2. The development of tight junctions between the bladder epithelial cells was investigated by incubating the tissue with solutions containing 1 m
M‐LaCl3 on the mucosal surface. No penetration of the junctions by lanthanum was observed in foetuses of 90 days or older. In younger bladders, the epithelial layer was stripped by treatment with lanthanum, but tight junctions appeared to be fully developed in early bladders incubated without lanthanum.

3. The surface structure of the luminal (mucosal) plasmalemma was fully developed at 50 days.

4. Unidirectional fluxes of labelled sodium and water were measured with identical solutions bathing the two surfaces of the bladder wall. No net water movement occurred; the mean ratio of efflux to influx in nine bladders was 1·002 ± 0·039 (
S.E. of mean). Under these conditions, the flux ratio for sodium was 1·735 ± 0·143 (
S.E. of mean) in twelve bladders.

5. Antidiuretic hormone (ADH) had no effect on net water movement but reduced the net efflux of sodium so that the flux ratio became 1·285 ± 0·255 (
S.E. of mean) n = 8. ADH also had a striking effect on the structure of the epithelium, causing marked swelling of the intercellular spaces. The tight junctions remained an effective barrier to lanthanum penetration under these conditions; lanthanum was not observed in the enlarged spaces.
Determination of membrane potentials in human and Amphiuma red blood cells by means of a fluorescent probe
Authors: Hoffman J. F. , Laris P. C.
Published: December 2014

1. Changes in the fluorescent intensity of the dye, 3,3′‐dihexyl‐2,2′‐oxacarbocyanine, added to suspensions of human and Amphiuma red blood cells were measured in parallel with changes in the membrane potentials of these cells. In these studies the membrane potential was altered in three different ways: by the addition of valinomycin to alter the ratio, PK/PCl, by a change in the pH of the medium to alter the ratio, Clc/Cl0, and by the substitution of impermeant anions for Cl0 again to alter the ratio, Clc/Cl0. In each case hyperpolarization led to a decrease and depolarization to an increase in fluorescent intensity.

2. The change in fluorescence with the addition of valinomycin was dependent on the concentration of K in both the cells and the medium. Changes in fluorescence were not observed when valinomycin was added to suspensions of frozen‐thawed, haemoglobin‐free ghosts with dye in KCl or NaCl solutions. Such changes were observed with reconstituted ghosts provided that there was a K concentration gradient across the membrane.

3. From values of cellular K and the corresponding external K concentrations for which there were no changes in fluorescence with valinomycin, estimations of membrane potentials were made. The potential was −5 to −8 mV for the human red cell and −19 mV for Amphiuma. These values are in good agreement with the potentials estimated from the Cl ratios (−9 mV for human and −17 to −20 mV for Amphiuma) and from those obtained by direct electrical measurements (−15 mV for Amphiuma).

4. Fluorescent intensity of the dye in suspensions of human red cells was shown to be a linear function of the log Clc/Cl0.

5. The dye (2·9 × 10−6
M) increased the inward rate constants for 24Na (3‐4‐fold) and 42K (0·5‐2‐fold) for human red cells. In addition, the dye was found to be haemolytic (5–6% in 1 hr) at 22° C.

6. In contrast, the dye did not alter the rate of 35SO4 efflux at 37° C from human red cells previously equilibrated with a Cl‐free SO4 medium.

7. The dye was also seen to interact with certain impermeant anions and other compounds, e.g. inhibitors of anion permeability, of interest. These interactions and other limitations of the use of this dye are discussed.
Temperature sensitivity of the paw of the cat: a behavioural study
Authors: Finger Stanley , Norrsell Ulf
Published: December 2014

1. Cats were trained to respond to differences between the temperatures of the floors of two corridors of a modified T‐maze for a food reward.

2. The cats were able to respond to differences between warm temperatures or differences between cool temperatures in the range of 1° C.

3. Both warm and cool discriminations were mediated by receptors located in or near the footpads.

4. The paw of the cat thus appears to be more sensitive to temperature changes than was believed previously, and its temperature sensitivity may be comparable to that of the hand of the primate.
On facilitation of transmitter release at the toad neuromuscular junction
Authors: Balnave Ron J. , Gage Peter W.
Published: December 2014

1. The time dependence of the increase in amplitude (facilitation) of a second end‐plate potential (e.p.p.) elicited within 10–100 msec of a preceding e.p.p. was examined at neuromuscular junctions in sartorius muscles of toads. Facilitation was defined by two characteristics, initial facilitation and the time constant of its exponential decay.

2. The time constant of decay of facilitation was longer at lower temperatures and the Q10 was 4·3 in the range 10–25° C. There was no significant effect of temperature on initial facilitation.

3. Ouabain (10−4‐10−3
M), lithium substitution for sodium, sodium azide (5 m
M) and N‐ethylmaleimide (NEM, 0·1 m
M) initially had no effect on initial facilitation or the decay of facilitation. After some time, they all caused a longer time constant of decay of facilitation and a depression of initial facilitation.

4. It was concluded that the decay of facilitation is not directly dependent on active transport of sodium ions, calcium efflux, ATP‐dependent movements of calcium or mitochondrial uptake of calcium following an action potential.

5. Ouabain, lithium, sodium azide, and NEM all caused an increase in transmitter release. This effect, and the late effects on facilitation, were thought to be due to an increase in intracellular calcium concentration in nerve terminals.

6. No relationship was found between the quantal content of e.p.p.s (range, 0·8‐100) and initial facilitation, or the time constant of decay of facilitation.

7. Substitution of strontium for calcium ions caused a marked prolongation of the time constant of decay of facilitation, and a depression of initial facilitation.

8. The results were consistent with the hypothesis that the time constant of decay of facilitation is related to the rate of disappearance of an ‘active’ complex of calcium (CaA) which, of itself, is not sufficient for transmitter release. It is suggested that an action potential produces CaA which decays with the time constant of facilitation and CaS, a short‐life complex of calcium which decays with the time constant of the phasic release of transmitter. The release of transmitter is proportional to some function of [CaA] and [CaS].
Twitch potentiation by potassium contractures in single muscle fibres of the frog
Authors: Chiarandini D. J. , Stefani E.
Published: December 2014

1. The modifications of isometric twitches after K contractures have been studied in single muscle fibres from frog muscles.

2. The twitch was greatly enhanced and somewhat prolonged after a conditioning K contracture. This potentiating effect was more evident in fibres having low values of the ratio control twitch tension/tetanus tension (P/P0).

3. In most of the fibres, the time course of the decay of the potentiation phenomenon could be represented by the sum of three negative exponentials with average half‐times of 9·1, 40 and 485 sec.

4. Between 3 and 10 min after the onset of the twitch potentiation the resting potential and action potential were unchanged.

5. Mn blocked the K contractures and prevented the onset of the twitch potentiation.

6. 40–140 sec after inducing a K contracture with 30 or 40 m
M‐K, a second exposure to the same [K] evoked a tension equivalent only to 57% of the first one. This partial refractoriness of the fibres is not seen when both contractures were elicited with 190 m
M‐K, and contrasts with the full recovery and potentiation of the twitch after a K contracture.
Interactions leading to horizontal cell responses in the turtle retina
Authors: Fuortes M. G. F. , Simon E. J.
Published: December 2014

1. Small responses to large fields of dim monochromatic lights were recorded intracellularly from luminosity horizontal cells (L‐cells), chromaticity horizontal cells (C‐cells) and cones in the retinae of turtles, Pseudemys scripta elegans.

2. Responses of cones to brief flashes applied over steady backgrounds were studied in order to interpret the corresponding responses of horizontal cells. Steady red or green backgrounds make the responses of red‐sensitive cones smaller, faster and often diphasic. Green backgrounds have similar effects on the responses of green‐sensitive cones to green flashes, but red backgrounds do not change them appreciably. Responses of double cones have properties intermediate between those of red and green cones.

3. L‐cells of both type I and type II are hyperpolarized by all visible wave‐lengths, and their spectral sensitivity in the linear range resembles that of red cones. Their responses are not invariant with respect to colour, and their sensitivity to green relative to red stimuli increases during red backgrounds. These properties suggest that L‐cells are activated mainly by red cones but also receive impingement from the red members of double cones.

4. Spectral properties of red/green C‐cells resemble those of green cones as modified by the recurrent action of L‐cells. They can be explained assuming that red/green C‐cells receive their principal impingement from green cones and subsidiary interactions from green/blue C‐cells and the green members of double comes.

5. The spectral sensitivity of the hyperpolarizing responses of green/blue C‐cells is ascribed to impingement from blue cones. Their depolarizing responses have complex properties which suggest that they are brought about by the activity of both L‐cells (probably through the blue cones) and red/green C‐cells.

6. It is concluded that the main properties of the responses of the horizontal cells can be explained by a simple circuit in which each horizontal cell is connected to a corresponding type of cone and the L‐cells have a recurrent impingement on all cones. The scheme is modified by additional interactions which operate on the responses of each horizontal cell type.
The dependence of evoked transmitter release on external calcium ions at very low mean quantal contents
Authors: Crawford A. C.
Published: December 2014

1. The mean quantal content of the frog end‐plate potential was examined under conditions that reduced evoked transmitter release to very low values.

2. When the calcium concentration of the Ringer is reduced below 10−4
M a deviation occurs from the fourth power dependence of the mean quantal content (m) on the calcium concentration such that more quanta are released than is expected from the behaviour of m at higher calcium concentrations.

3. At 10−5
M this extra quantal release is more than two orders of magnitude greater than that predicted by the fourth power relationship.

4. The calcium dependence of very low values of m was studied in low calcium Ringer in which the calcium was buffered by either citrate or EDTA. It was found that in the fourth power dependence of m on the external calcium concentration changes rather suddenly to an approximately linear dependence.

5. The inclusion of small concentrations of cobalt in the Ringer was found to reduce m to very low values even in the presence of millimolar concentrations of calcium.

6. The fourth power dependence of m on the external calcium concentration at high values of m was unaffected by the presence of cobalt. At low quantal contents the transition to a linear dependence on external calcium was again seen, but was shifted to calcium concentrations that did not require buffering.

7. The fourth power to linear transition is discussed in terms of its relevance to the relationship between m and the m.e.p.p. frequency.
The short range stiffness of active mammalian muscle and its effect on mechanical properties
Authors: Rack Peter M. H. , Westbury D. R.
Published: December 2014

1. The tension in tetanized cat soleus and lateral gastrocnemius muscles was measured during alternating lengthening and shortening movements. Sinusoidal movements were sometimes used; on other occasions the movement was at a constant velocity but with periodic reversal of direction.

2. With constant velocity movements of small amplitude the tension rose steeply during lengthening and fell during shortening in a relatively simple way. With longer movements the tension at first changed steeply as it had done with the smaller movement, but later in the movement the resistance of the muscles decreased so that the tension change became more gradual. The muscles resisted a small movement or the first part of a larger movement with a ‘short range stiffness’ which did not persist as the movement continued.

3. So long as the constant velocity movement was not too slow the short range stiffness was independent of velocity though it lasted for more of a fast movement than of a slow one.

4. In small movements the muscle was never extended beyond its short range stiffness, and the over‐all peak‐to‐peak tension change was therefore large compared with the amplitude of movement. When, with larger movements, the muscle was stretched into a range in which it became more compliant, the peak‐to‐peak force fluctuation did not increase by an equivalent amount, and over the whole course of the movement the force change per unit extension was smaller.

5. When the movement was confined to a short range, little work was expended in driving the muscle through a cycle of movement; its properties were essentially elastic. With larger amplitudes the muscle met the movement with a frictional resistance, the tension during lengthening then being greater than during shortening. A considerable amount of work had then to be done on the muscle to maintain the movement.

6. The short range stiffness was also apparent in the response to sinusoidal movements.

7. The short range stiffness was attributed to elastic properties of cross‐bridges between thick and thin filaments in the myofibrils.

8. The effect of the short range stiffness on the mechanical properties of the limb is discussed.
Active transport of iodide and other anions across the choroid plexus
Authors: Wright Ernest M.
Published: December 2014

1. An in vitro preparation of the frog choroid plexus was used to study mechanisms of anion transport.

2. It was observed that, in the absence of electrochemical potential gradients, there were net fluxes of I−, SCN−, TcO4−, and Br− across the plexus, from the ventricular to the serosal surface. The net flux of I− reached a maximum at a concentration of 250 μ
M.

3. On the basis of competition effects it was concluded that the affinity of the transport process for anions was: ClO4 > ReO4 ∼ BF4 > SCN ∼ SeCN > I > NO3 > Br > Cl.

4. Ouabain, oligomycin, phloretin and 2,4‐DNP inhibited the net transport of anions, but phlorrhizin, furosemide, 2,4,6‐trinitro‐m‐cresolate, reducing agents, and antithyroid agents did not. Ouabain and phloretin were only effective on the ventricular side of the preparation.

5. Anion transport required the presence of both Na and K. The requirement for Na was specific, but Rb, and to a lesser extent Cs, could substitute for K. Na in either the ventricular or the serosal fluids could partially stimulate anion transport, but K was only effective in the ventricular solution.

6. TcO4−, SCN− and I− were accumulated within the choroidal epithelium from the ventricular fluid, but not from the serosal fluid. Accumulation was inhibited by ouabain and ClO4−.

7. The unidirectional influx of I− across the apical cell membrane was about an order of magnitude greater than the flux across the epithelium. This flux was inhibited by ClO4−, ouabain, and Na‐free solutions.

8. These experiments suggest the following mechanism for anion transport across the plexus: anions are actively transported into the epithelium, by a ouabain sensitive, Na/K dependent pump located in the brush border membrane. The anions are accumulated within the epithelium, and, finally, they pass into the serosal fluid down their electrochemical potential gradient. Relations between anion transport, Na/K transport, and Na/K ATPases are discussed.
Effect of calcium and vasopressin on the response of frog skin to prostaglandin E1
Authors: Hall W. J. , Martin J. D. G.
Published: December 2014

1. Prostaglandin E1 increases sodium transport as measured by short circuit current (SCC) across isolated frog skin whereas calcium, added to the external Ringer fluid, decreases sodium transport. To help establish the site of action of prostaglandin the possible interaction of these two agents on sodium transport has been examined.

2. The effect of a standard dose of prostaglandin (0·5 × 10−6
M) on the short circuit current was tested on paired skins with either zero or high calcium (22·4 m
M) in the external Ringer fluid. In ten experiments the responses to prostaglandin (expressed in μA/cm2) were not significantly affected by external calcium.

3. In another series of experiments the chelating agent, EGTA, was included in calcium‐free external Ringer in order to promote greater depletion of skin calcium. The response of these skins to the standard dose of prostaglandin was of the same order of magnitude as that of control skins. The response was not sustained in contrast to that of normal skins and skins in high‐calcium fluids.

4. In a further series of experiments the reverse procedure was adopted whereby the response of the skin to low and high doses of calcium in the external Ringer was recorded in control conditions and when the skin had responded fully to twice the standard dose of prostaglandin. In addition, the calcium‐sensitive current was calculated for each skin in both circumstances. The latter was unchanged on addition of prostaglandin, and graded doses of calcium caused the same degree of inhibition of the short circuit current.

5. The results show no interaction between external calcium and prostaglandin and also no need for external calcium in prostaglandin stimulation of sodium transport.

6. The findings do not support the concept of chelation by prostaglandin of calcium from critical sites on the skin as the primary mechanism of its action on sodium transport. The results closely parallel those of a similar type of study into the relationship between vasopressin and external calcium on frog skin also.

7. When frog skin has responded fully to either prostaglandin E1 or vasopressin, it shows no response to the other, although removal of calcium from the external Ringer fluid causes a further increase in short circuit current.

8. Vasopressin causes a further increase in short circuit current in skins treated with prostaglandin F1α. Prostaglandin F1α may be a weaker agonist on frog skin than either vasopressin or prostaglandin E1.
A study of pace‐maker activity in intestinal smooth muscle
Authors: Connor J. A. , Prosser C. L. , Weems W. A.
Published: December 2014

1. Electrical activity of longitudinal muscle from cat intestine was recorded in the double sucrose gap.

2. Approximately 20% of the preparations demonstrated slow, spontaneous fluctuations of membrane voltage, slow waves. This activity, although quite uniform in a given preparation, showed considerable inter‐preparation variation with respect to amplitude, frequency and wave form.

3. Application of steady hyperpolarizing current decreased slow‐wave frequency and increased slow‐wave amplitude while depolarizing currents increased frequency and decreased amplitude.

4. Some preparations with no spontaneous slow‐wave activity developed slow waves when the membrane was hyperpolarized into a given range which, depending on the preparation, varied in size from 10 to 40 mV. Step or ramp depolarization of the membrane from hyperpolarized levels triggered slow waves in some preparations.

5. When the membrane potential of a slow‐wave generating preparation was clamped at the resting potential, spontaneous inward‐directed current transients were observed.

6. No changes in membrane conductance were observed during the course of a slow wave.

7. The slow‐wave pattern was simulated for individual preparations by applying the membrane current measured under voltage clamp to the passive membrane resistance and capacitance measured independently under current clamp.

8. In addition to the defined slow‐wave activity, voltage‐dependent oscillations in membrane potential were sometimes observed.

9. Application of 10−5
M ouabain irreversibly blocked slow waves and produced a membrane depolarization equal to or slightly greater than the slow wave crest. Repolarization of the membrane to the resting potential, or hyperpolarization, failed to restore slow‐wave activity.

10. Removal of external potassium produced a reversible sequence of events almost identical to those following ouabain application.

11. Replacement of 50% of the external sodium chloride with sucrose produced no changes in slow‐wave activity with respect to rates of rise or fall, maximum amplitude or frequency. Sucrose replacement of all external sodium chloride eliminated slow waves after 5 min; however, activity could be restored by a slight hyperpolarization. Longer exposures to the modified bath abolished activity.

12. Following a conditioning exposure to potassium‐free Krebs solution, readmission of potassium at normal concentration produced a mean hyperpolarization of 20·5 mV and in spontaneous preparations an arrest of activity.

13. Pump current in sodium‐loaded, non‐spontaneously active preparations was measured by voltage clamp and was observed to be voltage‐dependent.

14. The results of this study indicate that an electrogenic pump is present in longitudinal muscle of cat duodenum, and that oscillations in the level of pump current produce slow waves.