bluuebunny/crossref_metadata_2025 huggingface dataset:
Modification of the evoked release of noradrenaline from the perfused cat spleen by various ions and agents
Authors: Kirpekar S. M. , Prat J. C. , Puig Margarita , Wakade A. R.
Published: December 2014

1. Cat spleens were perfused with Krebs‐bicarbonate solution at a rate of about 7 ml./min at 33–35° C. Noradrenaline release after splenic nerve stimulation at 10 or 30 Hz was measured. Effects of various ions and drugs on noradrenaline release were determined.

2. Perfusion of phenoxybenzamine‐ and [3H]noradrenaline‐treated spleens with 1, 2·5 and 5 m
M cobalt or nickel—2 Krebs solution markedly reduced the release of noradrenaline by nerve stimulation. Lanthanum was the most potent inhibitor of noradrenaline release. Increasing the calcium concentration or adding tetraethylammonium chloride (TEA) partially counteracted the inhibitory effects of cobalt on release. Cobalt did not inhibit release induced by tyramine.

3. Calcium did not cause spontaneous release of noradrenaline either when high concentrations were injected directly into the spleen or after first perfusing the spleen with calcium‐free medium.

4. Carbachol, protoveratrine and high potassium inhibit, whereas TEA, barium and rubidium enhance, the evoked release of noradrenaline.

5. The relation of noradrenaline release to influx of calcium ions and its modification by various agents has been discussed.
Peritubular pH and transtubular potentials in isolated perfused cortical collecting ducts of rabbit kidney
Authors: Douglas R. J. , Isaacson L. C.
Published: December 2014

1. Cortical collecting ducts were dissected from slices of rabbit kidney, then perfused in vitro.

2. Transtubular electrical potentials were measured before and after abrupt changes in peritubular fluid pH.

3. Variation in peritubular fluid pH, induced either by alteration in HCO3− concentration or in H2PO4−/HPO42- ratio, produced biphasic responses in potential. Thus, reduction in pH caused an immediate fall, and then a prolonged and marked rise, in transtubular potential. The converse occurred on raising the pH.

4. Variation in luminal fluid pH between pH 4·85 and pH 7·35 did not alter this pattern of response.

5. In contrast to the above, reduction of peritubular fluid pH by elevation of pCO2 produced either no effect or a decrease in transtubular potential.

6. The transtubular potential of the cortical collecting duct appears to be a function of the pH gradient across some as yet unidentified part of the wall of the duct.
Excitation and inhibition of motoneurones in the tortoise
Authors: Rosenberg M. E.
Published: December 2014

1. Intracellularly recorded responses of lumbosacral motoneurones in the tortoise are described. The preparation was decerebrate and unanaesthetized. Cells were tested by stimulation of the main branches of the ipsilateral sciatic nerve.

2. The distribution of cells according to resting membrane potential is given; highest recorded values were around 70 mV.

3. The action potential has a step on the rising phase and has a total duration in the region of 4 msec.

4. The motoneurone input resistance, measured by the spike height method, was 5‐8 MΩ.

5. Orthodromic excitation of motoneurones occurred after a central latency of 2 msec.

6. Inhibition, and inhibitory (hyperpolarizing) potentials were demonstrated. Peak amplitude of maximum response was frequently greater than 10 mV. The potentials were influenced by injected currents in a manner resembling IPSPs in mammalian motoneurones. Minimum central latency for inhibitory potentials was about 3 msec.

7. Membrane potentials and dimensions of action potentials for motoneurones in the cat are given for purposes of comparison with the tortoise.
Inhibition of denervation changes in skeletal muscle by blockers of protein synthesis
Authors: Grampp W. , Harris J. B. , Thesleff S.
Published: December 2014

1. A study was made of the effects of inhibitors of protein synthesis (actinomycin D, chloramphenicol and cycloheximide) on the in vivo development of extrajunctional cholinergic receptors, tetrodotoxin‐resistant action potentials, slowing of the time course of the action potential, and on the fall in the resting membrane potential in denervated mouse skeletal muscle.

2. Actinomycin D (0·5 mg/kg,
I.P.) reduced the incorporation of uridine into skeletal muscle by 50–60% for 4‐5 days. There was no simultaneous reduction in
L‐leucine incorporation.

3. Actinomycin D (0·5 mg/kg
I.P., 1 day after denervation) inhibited the development of extrajunctional cholinergic receptors, tetrodotoxin‐resistant action potentials and the fall in resting membrane potential for approximately 4 days.

4. The post‐denervation fall in the maximum rate of rise and in the amplitude of the overshoot of the muscle fibre action potential was unaffected by actinomycin D treatment.

5. Actinomycin D failed to inhibit the appearance of the membrane changes if given later than 2 days after denervation.

6. Chloramphenicol (6 g/kg in divided doses) and cycloheximide (40 g/kg every 12 hr) were also able to inhibit the appearance of the membrane changes.

7. It is concluded that some denervation induced changes in the muscle fibre membrane depend on the synthesis of new proteins. The results imply that the motor nerve cell normally exerts a regulatory influence on the genome of the muscle cell.
The effect of external anions on steady‐state chloride exchange across ascites tumour cells
Authors: Aull Felice
Published: December 2014

1. The rate of cell chloride exchange, or efflux coefficient, was measured after equilibration in media of different anionic composition.

2. When sulphate substituted for chloride in the medium, the efflux coefficient was always higher than in control chloride solutions and varied inversely with external chloride concentration. In sulphate the chloride efflux coefficient varied from 19·6 to 100·7 hr−1. The mean control efflux coefficient was 6·60 ± 0·677 (
S.E. of mean).

3. In contrast, when external nitrate substituted for chloride, the efflux coefficient was independent of external chloride concentration and the same as in control chloride media. The mean value in nitrate was 6·42 ± 0·603 (
S.E. of mean). The results confirm findings of Hempling & Kromphardt (1965).

4. Steady‐state chloride flux varied in direct proportion to the external chloride concentration, which would be expected for passive chloride exchange. However, the slope of the line relating these variables was higher in sulphate than in nitrate and control media. Thus at any given external chloride concentration chloride flux was greater in sulphate than in nitrate and control solutions.

5. It is suggested that the effect of sulphate to increase cell chloride exchange may be related to its greater tendency to bind water, relative to chloride and nitrate.
Ion transport across an isolated preparation of sheep rumen epithelium
Authors: Ferreira H. G. , Harrison F. A. , Keynes R. D. , Zurich L.
Published: December 2014

1. The fluxes of isotopically labelled sodium, potassium and chloride passing in each direction across isolated sheets of rumen epithelium from the sheep have been measured under short‐circuit conditions.

2. With both sides of the epithelium bathed in chloride Ringer the mean sodium fluxes were 2·85 μmole/cm2.hr from rumen to blood and 1·28 μmole/cm2.hr in the reverse direction. In sulphate Ringer the sodium fluxes were 1·64 μmole/cm2.hr from rumen to blood and 0·54 μmole/cm2.hr from blood to rumen.

3. In chloride Ringer the mean potassium fluxes were 0·18 μmole/cm2.hr from rumen to blood and 0·54 μmole/cm2.hr from blood to rumen. In sulphate Ringer the potassium fluxes were 0·07 μmole/cm2.hr from rumen to blood and 0·35 μmole/cm2.hr from blood to rumen.

4. In chloride Ringer the mean chloride fluxes were 4·89 μmole/cm2.hr from rumen to blood and 3·78 μmole/cm2.hr from blood to rumen.

5. In chloride Ringer the mean value of the short‐circuit current was 13 μA/cm2, corresponding to a flux of 0·49 μequiv/cm2.hr. When sulphate was substituted for chloride, the short‐circuit current was increased by about 40%, and the net flux of sodium from rumen to blood fell by 30%.

6. Neither the sodium nor the chloride fluxes changed significantly when the epithelium was temporarily open‐circuited.
Changes in the intestinal transport of sodium induced by exposure of goldfish to a saline environment
Authors: Ellory J. C. , Lahlou B. , Smith M. W.
Published: December 2014

1. The uptake and transflux of sodium by goldfish intestines has been compared under different experimental conditions. Uptake was measured from a 1 min contact of the intestinal mucosa with radioactive sodium chloride solution. Transflux was measured over a period of 2 hr using the everted sac technique.

2. Keeping goldfish in saline reduced the transflux of sodium to one quarter the value found for fresh‐water fish. The uptake of sodium was halved by this treatment. Cortisol injected previously into saline‐adapted fish changed neither the transflux nor the uptake of sodium measured subsequently.

3. In fresh‐water fish hypophysectomy reduced sodium transflux while leaving the uptake of sodium unchanged. Injection of cortisol restored sodium transflux to control levels without producing any additional effects on the uptake of sodium.

4. It is suggested that adaptation to saline involves regulation of sodium movement across the microvillar membrane of the mucosal cell. Cortisol would appear to play no part in this type of regulation.

5. The presence of cortisol, or possibly other steroids with similar actions, has however been shown to be essential for the normal operation of sodium transport in this tissue. It is not clear exactly how cortisol exerts this effect. What evidence there is suggests that cortisol exerts a metabolic control rather than changing directly the membrane permeability of the cell.
Intracellular calcium movements in skinned muscle fibres
Authors: Ford L. E. , Podolsky R. J.
Published: December 2014

1. Force development and 45Ca movement between the internal membranes and the myofilament space were measured in segments of skinned muscle fibres.

2. At 20° C calcium ions in the myofilament space of calcium loaded fibres caused the internal membranes to release a substantial amount of calcium which produced a large force spike. Calcium produced a similar force spike in fibres containing only the physiological level of calcium when the temperature was lowered to about 6° C.

3. The force spike at 6° C was inhibited when the magnesium concentration in the bathing solution was increased from 1 to 6 m
M. The pattern of force development in preparations transferred directly from oil to a free calcium solution indicated that the normal concentration of Mg2+ in the myofilament space of intact fibres is of the order of 10−3
M.

4. A possible role for the regenerative calcium release mechanism in the physiological activation of muscle fibres is suggested.
The effect of voltage on the time course of end‐plate currents
Authors: Magleby K. L. , Stevens C. F.
Published: December 2014

1. End‐plate currents have been studied in glycerol‐treated frog sartorius nerve—muscle preparations with the voltage clamp technique.

2. End‐plate currents follow a simple exponential time course over most of their declining phase.

3. The rate constant α that characterizes this exponential decay depends upon membrane potential V according to the relationship α (V) = BeAV, with A = 0·00795 ± 0·00043 (
S.E.) mV−1 and B = 1·67 ± 0·04 (
S.E.) msec−1.

4. Voltage sensitivity decreases (that is, A in the above equation becomes smaller) as the recording and current‐passing electrodes are moved away from the end‐plate region.

5. The voltage sensitivity of α is decreased by decreasing the gain of the voltage clamp amplifier.

6. Changing the end‐plate current amplitude by curare treatment, by increased calcium ion concentration, and by facilitation and depression has essentially no effect on end‐plate current time course.

7. When membrane potential is changed step‐wise during the decaying phase of the end‐plate conductance change, currents begin to decline with a rate constant α appropriate to the new membrane potential in less than 0·2 msec.

8. Treatment with prostigmine methylsulphate in concentrations up to 50 μg/ml. slows end‐plate current decay but has little effect on voltage sensitivity. That is, B in the above equation is decreased by prostigmine treatment, but A is relatively unaffected.
The interactions of fibrinogen and dextrans with erythrocytes
Authors: Rampling M. , Sirs John A.
Published: December 2014

1. The rate of packing of erythrocytes in whole blood, under a centrifugal field of 200 g, has been studied using an automatic recording centrifuge.

2. Reduction of the supernatant fibrinogen concentration, by repeatedly washing the cells, lowers the rate of packing and reduces the cell flexibility.

3. Resuspending the cells in their own plasma or in isotonic solutions containing fibrinogen restores their flexibility.

4. Rouleaux formation has been shown to have no effect on the rate of packing by comparison of blood diluted with plasma, isotonic NaCl or Ringer—Locke solutions. While the degree of rouleaux formation varied with the diluent used, the rate of packing and packed cell haematocrit were the same, for the same dilution.

5. Both formalin and dextran altered the degree of rouleaux formation and reduced erythrocyte flexibility. Dextran was found to act indirectly on the erythrocyte flexibility by reducing the plasma fibrinogen concentration.
Release of transmitters on stimulation of the nucleus linearis raphe in the cat
Authors: Ashkenazi Ruth , Holman R. B. , Vogt Marthe
Published: December 2014

The nucleus linearis intermedius raphe and the nucleus linearis rostralis were stimulated during the perfusion of the anterior horn of the right lateral ventricle of anaesthetized cats. Whereas release of 5‐hydroxytryptamine (5‐HT) was consistently obtained, there was no release of acetylcholine (ACh).

The independence of the release of 5‐HT from that of ACh was seen both during low basal release of ACh (rising base line), and during the period when a plateau of resting release had been reached. It was also demonstrated in experiments in which the same perfusate was examined for both compounds.
Direct intracellular pH measurement in rat and crab muscle
Authors: Paillard Michel
Published: December 2014

1. Conflicting values of intracellular pH (pHi) were obtained by Caldwell in crab muscle and by Carter et al. in rat muscle. To investigate this discrepancy, double and single barrelled pH sensitive micro‐electrodes as described by Carter et al. were used both in rat muscle (in vivo and in vitro) and in large single fibres of crab (in vitro).

2. The pHi values obtained in the superficial layers of muscle cells in rat and pHi values obtained in the superficial area of large single fibres in crab seemed in agreement with the Donnan equilibrium. Furthermore, when the membrane potential (Em) value of extracellular pH (pHe) value was changed, each new pHi value was obtained instantly.

3. The pHi values obtained in deep layers of muscle cells in rat (pHi 6·68) and in a deep area of large single fibres in crab (pHi 6·96) did not agree with Donnan equilibrium; these pHi values were little influenced by modifications in Em or pHe values.

4. These findings could be easily explained if the length of the sensitive portion of the pH micro‐electrode exceeds the diameter of rat muscle cells and is smaller than the diameter of crab large fibres. The pHi values obtained superficially in the two preparations and which seem in agreement with the Donnan equilibrium are artificially low because the Em values recorded by the pH micro‐electrodes are partly shunted.
The effect of previous dietary intake of calcium on calcium absorption in rats
Authors: Kemm J. R.
Published: December 2014

1. The effects are described of the calcium content of diets with a calcium: phosphate ratio of 1 fed to rats during the preceding 6 weeks on aspects of calcium and phosphate metabolism during the seventh week. The apparent absorption of calcium and phosphate, the urinary excretion of calcium and phosphate, the amounts of calcium and phosphate in the carcass and the fasting serum calcium were studied.

2. Apparent absorption of calcium and phosphate decreases the longer an animal is on a high calcium diet and the more calcium there is in that diet. Under the same conditions urinary excretion of calcium is increased while urinary excretion of phosphate remains constant.

3. The percentage of calcium and phosphate in the carcass is greater the longer an animal is on a high calcium diet and the more calcium there is in the diet, but dietary changes do not affect the serum calcium.

4. Apparent absorption of calcium is not correlated with serum calcium but is significantly correlated with percent carcass calcium.

5. A distinction is drawn between the effect of the diet currently being consumed (kinetic effect) and the effect of the diet consumed previously (adaptation).

6. Changes in apparent absorption of calcium have a greater effect on calcium retention than on changes in urinary excretion.

7. The mechanism bringing about the changes in absorption is discussed and it is concluded that serum calcium is unlikely to be the monitored parameter which detects the need for greater absorption; parathyroid hormone is probably not involved.
The dependence of the latency relaxation on sarcomere length and other characteristics of isolated muscle fibres
Authors: Mulieri Louis A.
Published: December 2014

1. The latency relaxation has been examined in single fibres from frog striated muscle with particular attention given to its possible relation to Ca2+ release during excitation—contraction coupling.

2. Latency relaxations were recorded at 19–23° C from massively stimulated (0·2 msec pulses) single fibres using two selected RCA 5734 transducer tubes in a bridge circuit.

3. The depth of the latency relaxation has its full value when stimulus strength is between 40 and 400% above twitch threshold. Stronger stimuli reversibly diminish the latency relaxation.

4. The variation in depth of latency relaxation with sarcomere length was found similar to that reported previously for multifibre preparations but in single fibres the peak of the curve consists of a plateau between sarcomere lengths of 2·8 μ and 3·2 μ.

5. Sucrose hypertonicity increases the depth of the latency relaxation at sarcomere lengths below 2·8 μ but above this length it has either no effect or a depressant effect depending on the degree of hypertonicity.

6. The maximal depth of the latency relaxation (measured at 3 μ) averaged 0·23% of the maximal tetanus tension (measured at 2·2 μ) and was strongly correlated (r = 0·87) with the latter in forty‐five single fibres.

7. The maximal depth of the latency relaxation is not correlated with the number of sarcomeres in series in a fibre.

8. The results of this study are shown to fully support and extend Sandow's (1966) hypothesis that the latency relaxation is caused by release of activator Ca2+ from the sarcoplasmic reticulum.
Factors affecting the maturation of glomerular filtration rate and renal plasma flow in the new‐born dog
Authors: Kleinman Leonard I. , Lubbe Ronald J.
Published: December 2014

1. The maturation of glomerular filtration rate was studied by comparison of thirty‐six new‐born mongrel dogs aged 1–35 days with six adult dogs.

2. Under mannitol diuresis, glomerular filtration rate (GFR) rose from 0·16 ml. min−1.g kidney−1 at 1 day of age to 0·34 ml. min−1.g kidney−1 at 1 month of age. Adult GFR averaged 0·68 ml. min−1.g−1. There was good correlation of GFR with arterial blood pressure (r = 0·76, P < 0·001). Part of the statistical correlation of GFR with blood pressure was found to be independent of the relationship between blood pressure and age.

3. Acute increases or decreases in blood pressure resulted in parallel changes in GFR in the puppies. There was no change of GFR with change of blood pressure in adult dogs. Carotid artery clamping, independent of blood pressure changes, produced increased renal vascular resistance and decreased GFR in the pups.

4. Renal plasma flow (RPF) increased from 0·70 ml. min−1.g−1 at 1 day of age to 1·80 ml. min−1.g−1 at 1 month and showed good correlation with blood pressure (r = 0·67, P < 0·001). Filtration fraction (GFR/RPF) and renal vascular resistance did not vary with age in the pup and were the same as those for the adult.

5. These results support the hypothesis that maturation of GFR and RPF are closely related to maturation of arterial blood pressure in the mongrel dog. The factors other than blood pressure which also affect renal maturation in the dog still need to be more clearly defined.
Factors affecting the maturation of renal PAH extraction in the new‐born dog
Authors: Kleinman Leonard I. , Lubbe Ronald J.
Published: December 2014

1. The maturation of renal para‐amino‐hippurate extraction (EPAH) was studied in thirty‐nine mongrel new‐born dogs aged 2–29 days. EPAH was also measured in five adult dogs for comparison.

2. There was no apparent change of PAH extraction during the first month of life but EPAH was lower in the puppy than in the adult. Under mannitol diuresis EPAH averaged 0·49 for the puppies and 0·83 for the adult dogs (P < 0·001). EPAH averaged 0·48 for the puppies under nondiuretic conditions, a value not significantly different from that observed during mannitol diuresis. There was no correlation of EPAH with mean arterial blood pressure.

3. Inulin extraction (EIn) remained constant during the first month of life and was the same in the new‐born and adult dog suggesting that preglomerular shunting of plasma away from functioning nephrons was the same for both the puppy and adult dog.

4. EPAH did not change in the puppy when plasma concentrations varied from trace (using [3H]PAH) to 0·25 m
M indicating that excessive PAH load is not a factor in the low EPAH of the puppy.

5. Diffusion of PAH from the red blood cell was excluded as an explanation for the low EPAH since diffusion was the same for both the adult and new‐born dog.
The time course of potassium contracture of single muscle fibres
Authors: Caputo Carlo
Published: December 2014

1. At 3° C the long duration of potassium contractures and the delay in the repriming process allow one to carry out solution changes while the responses are still in progress, making it possible to study the processes that determine the contracture time course.

2. The contractures can be cut short by suddenly lowering the external potassium concentration to normal values. Re‐exposure to the high potassium medium causes the fibres to redevelop tension, in a way that depends on the time at which the original response was interrupted.

3. The period of interruption can be prolonged beyond the duration of the original contracture without affecting the second response. This redevelopment of tension is not associated with repriming since this process is much delayed. For thirty‐five interrupted contractures the mean of the sum of the time integrals of tension in the two responses amounts to 98% of the mean of the time integral of tension in the uninterrupted contractures.

4. Addition of tetracaine or removal of calcium also causes the fibre to relax from a potassium contracture, although at a slower rate than that obtained by lowering the external potassium concentration. In these cases, however, no tension is redeveloped when the standard contracture medium is reapplied. When calcium in the contracture medium is replaced by nickel, the contracture time course is not diminished.

5. The results obtained with potassium contractures clearly show that the contractile activator is released continuously during a contracture. The prolonged time course of contractile responses in the cold can be explained at least in part by a prolonged release of calcium. There are no reasons to believe that at low temperature there is more activator available for release, and therefore it can be concluded that in the cold release of calcium proceeds at a slower rate.

6. Release of calcium is under control of the membrane potential, and its time course can be determined either by a fixed store of available calcium that is depleted or by a membrane mechanism which is activated upon depolarization and later inactivates with time. The evidence obtained in the present work does not allow one to decide in favour of one of these two possibilities. However, the fact that contractures are prolonged in the cold, and the finding that repriming is delayed, can be utilized in further studies to clarify the mechanism that controls the release of calcium.
Sodium dependence of the inward spread of activation in isolated twitch muscle fibres of the frog
Authors: Bezanilla F. , Caputo C. , Gonzalez‐Serratos H. , Venosa R. A.
Published: December 2014

1. The excitatory process travelling along the T‐system may be either electrotonic or regenerative. If Na+ dependent action potential is present in the tubular membranes, high frequency of stimulation might cause a Na+ depletion in the tubules sufficient to abolish this process.

2. We tested this hypothesis by recording tension in isolated muscle fibres stimulated tetanically (up to 60 shocks/sec). In low [Na+] solutions, output tension was initially similar to that in normal Ringer, but then fell smoothly to a substantially lower value.

3. The activity of individual myofibrils was recorded directly with ciné‐micrographs during isotonic contractions while the fibres were stimulated at high frequencies. In low [Na+]o wavy myofibrils appeared in the centre of the fibre and spread towards the periphery, indicating failure of activation. Wavy myofibrils never appeared in normal Ringer.

4. Intracellular action potentials recorded during the tetanic stimulation indicated that the inactivated myofibrils present in low [Na+] solutions cannot be explained by the changes in size and duration of the action potential.

5. Our results strongly suggest the existence of a regenerative Na+ conductance in the tubular membrane during the inward spread of an excitatory process.
Transport of calcium in the perfused submandibular gland of the cat
Authors: Nielsen S. Pors , Petersen O. H.
Published: December 2014

1. In the perfused cat submandibular gland efflux and influx of 45Ca, and concentrations of K, 40Ca and Mg in the effluent from the gland were measured under different experimental conditions.

2. When the standard perfusion fluid was shifted to a high Mg (5 m
M) or a low Ca (0·25 m
M) solution the efflux of 45Ca from the pre‐labelled gland declined. The magnitude and the duration of the effect of the high Mg concentration was more marked at a low external Ca concentration and was abolished by Mersalyl (1 m
M). When the standard perfusion fluid was shifted to a Mg‐free solution the efflux of 45Ca from the pre‐labelled gland increased.

3. After shift of 45Ca containing perfusion fluid from normal to a high Mg (5 m
M) solution the influx of 45Ca to the gland increased rapidly.

4. Both acetylcholine (ACh) and adrenaline caused a marked increase in the efflux of 45Ca from the pre‐labelled gland. This increase in efflux was also seen under conditions where the gland was unable to secrete, i.e. during perfusion with Ca‐free and Na‐free tetraethylammonium Locke solutions.

5. Stimulation with ACh failed to reveal any rapidly occurring increase in influx of 45Ca.

6. Stimulation with ACh evoked a small temporary increase in the concentration of 40Ca. and Mg in the effluent.

7. It is suggested that Ca uptake by intracellular Ca‐accumulating systems of the submandibular gland depends on the external Mg concentration and that ACh and adrenaline cause a release of Ca bound intracellularly.
Heat production and fluorescence changes of toad sartorius muscle during aerobic recovery after a short tetanus
Authors: Becker Anne Godfraind‐De
Published: December 2014

1. The time course of the aerobic recovery following a 0·5 sec tetanus at 20° C of the sartorius muscle of the toad Bufo bufo, equilibrated in bicarbonate‐CO2 Ringer solution, has been followed by recording simultaneously the heat production and the fluorescence excited by ultra‐violet light at 366 nm.

2. The fluorescence light emitted in these conditions in the region of 450 nm monitors the state of oxidation‐reduction of the nicotinamideadenine dinucleotides (NAD+‐NADH). After a short tetanus, the cycle evoked consists of an initial increase of the fluorescence (reduction of NAD+) followed by a long lasting phase of decreased light emission. This includes an early period of oxidation of NADH succeeded by a slow reduction of the NAD+ formed in excess over the resting state. After iodoacetate, the initial reduction is suppressed.

3. The time course of both fluorescence and heat production may be analysed into a rapid and a slow component by a double exponential model.

4. The time courses of the aerobic recovery heat and of the fluorescence changes are similar after five minutes, but differ in their fast components. IAA significantly increases the rate constants of the fast terms of both monitors.

5. The slow component is mainly related to aerobic processes while the fast one is due to both oxidative and glycolytic reactions occurring simultaneously.
The effects of anaesthetics on synaptic excitation and inhibition in the olfactory bulb
Authors: Nicoll Roger A.
Published: December 2014

1. The effects of anaesthetics (pentobarbitone, hexobarbitone, halothane, urethane, chloralose, chloral hydrate and ethanol) on the extracellular field potentials of the olfactory bulb produced by lateral olfactory tract stimulation were analysed.

2. Relatively large doses of all the anaesthetics (e.g. pentobarbitone, 40–70 mg/kg) depressed the synaptic excitation of granule cells.

3. The antidromic invasion of mitral cell dendrites was only slightly less sensitive to the anaesthetics than was the synaptic excitation of granule cells.

4. A wide dose range of anaesthetics (e.g. pentobarbitone, 3–60 mg/kg) prolonged the granule cell post‐synaptic inhibition of mitral cells. All the anaesthetics, except ethanol, prolonged the inhibition.

5. The action of anaesthetics on post‐synaptic inhibition was due to a specific effect on the inhibitory synapses.

6. Amino‐oxyacetic acid, an inhibitor of GABA catabolism, had little effect on the synaptic inhibition or on the ability of hexobarbital to prolong the inhibition. This suggests that the prolongation seen with anaesthetics is not a result of interfering with GABA catabolism.

7. The present results are compared with results obtained with anaesthetics in other areas of the nervous system and it is proposed that prolongation of ‘gaba‐ergic’ inhibition might contribute to an agent's ability to produce general anaesthesia.
An investigation of spontaneous potentials recorded from the smooth‐muscle cells of the guinea‐pig seminal vesicle
Authors: Kajimoto N. , Kirpekar S. M. , Wakade A. R.
Published: December 2014

1. A spontaneous discharge of small potentials from smooth muscle cells of the guinea‐pig seminal vesicle has been described. The mean amplitude, frequency and duration of the potentials were 0·9 mV, 12·2/min, and 92 msec, respectively. Occasionally, large potentials of 5–7 mV were recorded.

2. The frequency of spontaneous potentials was enhanced by about twofold in 15 m
M potassium—Krebs solution. Removal of calcium from the perfusing solution, or adding excess magnesium (12 m
M) suppressed the rate of these potentials. Cobalt (2·5 m
M) did not affect them but blocked excitatory junction potentials evoked by the hypogastric nerve stimulation.

3. The spontaneous potentials were unaffected by atropine. Their rate and amplitude were reversibly reduced in the presence of high concentrations of phentolamine (10−4 but not by 10−5 g/ml.). Guanethidine enhanced the frequency initially (5 min), but subsequently the control rate was not appreciably changed, even after 20 min of guanethidine perfusion.

4. After post‐ganglionic denervation or reserpine treatment, the frequency of discharge of spontaneous potentials was reduced, without any effect on amplitude.

5. The properties of the spontaneous potentials recorded from the smooth muscle cells of the seminal vesicle are similar to those reported for the vas deferens. They appear to be due to an interaction between noradrenaline released from sympathetic nerve endings and the smooth‐muscle cell membrane. Present experiments cannot completely rule out the possibility that another transmitter in addition to noradrenaline may be released at this neuroaffector junction.
The heat of shortening during repeated tetanic contractions of muscle treated with 1‐fluoro‐2,4‐dinitrobenzene
Authors: Lebacq J.
Published: December 2014

1. The effect of repeated stimulation and of FDNB on the heat of shortening has been studied in sartorius muscles of Rana temporaria at 0° C.

2. The muscles were stimulated at 15 min intervals during 1·2 sec. During the plateau of tetanic activity, they were allowed to shorten 4·3 mm at constant velocity. After eight such contractions, they were poisoned with 0·4 m
M‐FDNB and the series continued.

3. From tetanus to tetanus, the tension during shortening decreased faster than the isometric tension; FDNB enhanced this effect. Despite a progressive decrease in the initial heat production, the heat of shortening did not change significantly in the normal muscle; immediately after poisoning it became larger, but from then on, it declined rapidly from tetanus to tetanus, faster than the over‐all heat production.

4. The first tetanus after FDNB is thus especially favourable when looking for a chemical counterpart of heat of shortening. On the other hand, the postulated development of a friction in the intoxicated muscle cannot explain the changes in mechanical and thermal properties of the muscle. This point is discussed.
Potassium ion accumulation near a pace‐making cell of Aplysia
Authors: Eaton D. C.
Published: December 2014

1. A delayed current decrease associated with prolonged depolarization was studied in R15 (the parabolic burster) of Aplysia by using intracellular recording and voltage clamp techniques.

2. For long duration command pulses (3 sec), the outward current shows a delayed decrease. The current goes from a maximum near 100 msec and falls until a steady‐state outward current is reached between 1·5 and 2·5 sec after the beginning of the command step. This final steady‐state current is usually only about 20–30% of the peak outward current.

3. Double step voltage clamps show that this current decrease is associated with a large shift of e.m.f. Measurements of conductance, on the other hand, fail to show any significant difference in conductance associated with peak and steady‐state currents.

4. From the results of application of high K+ ringer, the conclusion is reached that this shift in e.m.f. is due to an accumulation of K+ near the exterior cell membrane. Several other experiments exclude the possibility of either metabolic events or compensating conductance changes producing the phenomenon.

5. The location of the accumulation is considered on the basis of anatomical studies. It is concluded that the accumulation takes place in the extensive infoldings found in cells like R15. An explanation of the difference in delayed current decrease between pace‐makers and non‐pace‐makers is suggested, since the pace‐makers apparently have more extensive invaginations than the non‐pace‐makers. This suggestion is lent support by measurements of capitance and current density.
Binding of the cardiac glycoside ouabain to intact cells
Authors: Baker P. F. , Willis J. S.
Published: December 2014

1. Measurements were made of the binding of [3H]ouabain to a variety of cell types.

2. Two components of binding could usually be distinguished: a component that saturated at low glycoside concentrations and a component that increased up to the highest ouabain concentrations examined.

3. Detailed studies with HeLa cells and kidney slices from guinea‐pigs showed that the saturable component is probably associated with inhibition of the Na pump. The main evidence for this is (a) at low concentrations of ouabain there is a close correspondence between the concentration of ouabain giving half‐maximum binding and the concentration giving half‐maximum inhibition of the Na pump; (b) at low glycoside concentrations, binding precedes inhibition of the Na pump; (c) the rate of binding is very sensitive to external K ions, being highest in the absence of K; (d) binding is reversible and the release of ouabain is associated with reactivation of the Na pump, (e) binding is reduced in the absence of Na ions and in the presence of metabolic inhibitors; (f) binding has a Q10 of about 4; and (g) in the presence of Na and ATP, lysed HeLa cells bind a similar amount of ouabain and the binding is sensitive to K ions.

4. The linear component of binding does not seem to involve the Na pump and it may reflect uptake of ouabain into the cell interior. It has a Q10 of 2·5 and is unaffected by K concentrations which have a large effect on the saturable component.

5. Bound ouabain could be removed from HeLa cells by low pH, trichloroacetic acid, urea, high temperatures and 100% ethanol. These agents did not distinguish between the two components of binding.

6. Criteria are developed for estimating the number of Na pumping sites in cells and the data for ouabain‐binding to a number of cells is compared with the activity of the (Na + K)‐activated ATPase in the same tissues. Although the number of pumping sites varies from less than 1/μ2 to 1500/μ2 of membrane, the turnover at these sites seems to be fairly constant between 3,500 and 15,000 min−1 at 35° C.
Inhibition of the sodium pump in squid axons by cardiac glycosides: dependence on extracellular ions and metabolism
Authors: Baker P. F. , Willis J. S.
Published: December 2014

1. The rate of inhibition of the Na pump by ouabain was examined both by direct measurement of the rate of decline of the Na efflux and by the binding of [3H]ouabain.

2. The onset of inhibition of the Na efflux was concentration‐dependent; but did not follow simple first order kinetics. The time course of inhibition was roughly exponential although in about 30% of the axons inhibition was preceded by a transient stimulation of the Na efflux.

3. Inhibition of the Na efflux by both ouabain and strophanthidin was apparently irreversible.

4. The onset of inhibition was slowed markedly at low temperatures.

5. Replacement of external Na by choline, dextrose or potassium slowed the rate of inhibition. Li behaved like Na and inhibition was faster in K‐ASW than in choline‐ASW.

6. The rate of inhibition of Na‐Na exchange was similar to that of Na‐K exchange, but ouabain failed to bind securely to fully poisoned axons.

7. Two components of [3H]ouabain‐binding could be distinguished. A linear component which probably reflects uptake into the cells and a saturable component which seems to reflect binding to Na‐pumping sites.

8. The saturable component of binding followed a similar time course to the inhibition of the Na efflux and the rate of binding was reduced in choline‐ASW and in fully poisoned axons.

9. Measurements of [3H]ouabain‐binding indicate that the number of Na pumping sites in the axon membrane is probably between 103 and 104/μ2.
The effect of adenosine on the release of the transmitter from the phrenic nerve of the rat
Authors: Ginsborg B. L. , Hirst G. D. S.
Published: December 2014

1. The action of adenosine on neuromuscular transmission has been studied on the rat phrenic nerve—diaphragm preparation.

2. Adenosine (0·025–10 m
M) reversibly reduced the quantum content of end‐plate potentials and the frequency of miniature end‐plate potentials to about half the control values in preparations in which transmission was blocked with high Mg2+ and/or low Ca2+ concentrations. Where transmission was blocked with tubocurarine, the amplitude of end‐plate potentials was reduced to about half the control values by adenosine.

3. In solutions with very low Ca2+ concentrations (no added Ca2+ and 1 m
M‐EGTA) adenosine had a smaller effect on the frequency of miniature end‐plate potentials.

4. The effect of adenosine (0·025 and 0·05 m
M) was abolished by theophylline (1·8 m
M).

5. The results are discussed in relation to the increase in cyclic AMP in brain slices caused by adenosine and the abolition of this effect by theophylline (Sattin & Rall, 1970).
Potassium conductance changes in skeletal muscle and the potassium concentration in the transverse tubules
Authors: Almers W.
Published: December 2014

1. When one hyperpolarizes a muscle fibre by passing electric current, the K conductance declines with time. Voltage‐clamp experiments on frog sartorius muscle fibres showed that two components contribute to this decline.

2. A rapid component operates when the fibre is hyperpolarized to potentials more negative than −120 mV. Decline by this mechanism is reversed completely within 200 msec. The large effect of temperature on the kinetics of this process indicates that it represents a time‐dependent membrane permeability change.

3. A slow component operates also at less negative potentials. Recovery at −65 mV takes place with half‐times of about 0·4 sec. The Q10 for the rate of recovery is 1·3, indicating that this process is diffusion limited.

4. After prolonged hyperpolarization to potentials positive to −120 mV, membrane current at the resting potential is outward and persists for several seconds. At that time, the potential measured in the absence of membrane current is shifted in the negative direction by 3–5 mV.

5. This shift and the time course of currents near the resting potential after hyperpolarization as well as the Q10 of 1·3 indicate that the slow process is due to changes in tubular K concentration and not to a time‐dependent membrane permeability change.

6. At potentials less negative than −120 mV, tubular depletion can satisfactorily account for the decline of K conductance. At more negative potentials, the decline appears to be due to both depletion and a permeability change.
The effect of hyperventilation on maternal placental blood flow in pregnant rabbits
Authors: Leduc B.
Published: December 2014

1. In anaesthetized pregnant rabbits near term, cardiac output and its distribution were measured by injection of isotope‐labelled microspheres. Hypocapnia (mean arterial PCO2 18 mm Hg), induced by intermittent positive pressure hyperventilation, caused a 43% reduction in maternal placental blood flow, attributed mainly to vasoconstriction. Myometrial flow was not significantly changed.

2. Moderate hypercapnia (mean arterial PCO2 46 mm Hg) caused no change in placental flow, compared with observations made while breathing air spontaneously (PCO2 31 mm Hg).

3. Intravenous infusions of adrenaline or noradrenaline 1 μg/kg. min caused maternal placental vasoconstriction.

4. During the especially warm summer of 1969, there was a mean 46% reduction in maternal placental blood flow in pregnant rabbits near term, breathing room air spontaneously with normal blood gas values and rectal temperatures. This was associated with an increase in the number of runts and dead foetuses.
Rhodopsin bleaching signals in essential night blindness
Authors: Alpern M. , Holland M. G. , Ohba N.
Published: December 2014

1. The dark‐adaptation curves of two subjects with essential night blindness revealed no evidence for functioning rod vision. Cone vision was normal.

2. The photopupillomotor dark adaptation, and flash intensity response amplitude curves on one of these subjects confirmed the absence of rod function.

3. However, there is the normal amount of rhodopsin in their rods with normal kinetics.

4. Cone pigment kinetics are also nearly normal. After a full bleach, log threshold elevation of the foveal cones is linearly related to pigment regeneration. The constant of proportionality is about 3·0 as it is in the normal retina.

5. After a full rhodopsin bleach, the contralateral pupil size recovered its full dark value along a curve which followed the regeneration of rhodopsin.

6. The results in (5) are identical to those previously found on normal subjects.

7. With the exception of a very small response attributed to the contribution of cones, no significant changes in pupil size were evoked by uniform ganzfeld steady backgrounds until the intensity of retinal illuminance was so high that appreciable rhodopsin was bleached. This contrast to the changes evoked by weak steady backgrounds in the normal eye.

8. Therefore, rod bleaching signals are normal in such retinas but rod signals evoked by real lights are not functional. This supports Rushton's concept as to how bleaching signals influence retinal sensitivity as opposed to the view of Barlow.

9. The defect in essential night blindness very probably involves the rod automatic gain control, but because of (4) the cone gain control must be normal.

10. Therefore, rod and cone gain control mechanisms must be independent in these night blind retinas and, by analogy, in the normal retina as well.
The extent of the destruction, during passage through the lungs, of a substance secreted by the heart
Authors: Lockett Mary F. , Retallack R. W. , Sayers Linda
Published: December 2014

1. In vitro, the lungs of male Wistar rats, 220–230 g, removed heart substance (HS) from saline perfusates. HS could not be recovered by subsequent perfusion with HS free solution.

2. A maximum rate of HS‐uptake, 8·5 ng biological equivalents of 18‐monoacetate of
D‐aldosterone (18 MA)/min, was reached at a concentration of HS equivalent to 3·5 ng 18 MA/ml. at a flow of 6 ml./min.

3. Uptake was not significantly affected by a fall in temperature from 38 to 18–20° C or by reduction in PCO2 to zero. Uptake was reduced by anoxia and was enhanced by decrease of pH from 7·4 to 6·6.

4. 30% of the HS taken up by the lungs at 20° C was recoverable: none of the HS taken up at 38° C was recovered.

5. Uptake of HS by binding is considered rate‐limiting to the destruction of HS in the lungs.

6. The concentrations of HS found in the pulmonary and carotid arterial blood of cats under chloralose anaesthesia, during haemorrhage, were biologically equivalent to 1098 ± 38·7 and 169 ± 13·4 ng 18 MA/100 ml. (means ±
S.E.) respectively, in four experiments.
Cholinergic mechanisms in the rat somatosensory cerebral cortex
Authors: Stone T. W.
Published: December 2014

1. The responses of identified cells in the rat cerebral cortex to cholinomimetic and anticholinergic substances has been investigated.

2. Acetylcholine and muscarinic agonists have an excitatory action on 80% of pyramidal tract cells. This response is found especially on cells responding to specific thalamic stimulation and the burst of spikes evoked from this site can sometimes be blocked by the iontophoresis of atropine. This strongly suggests an excitatory transmitter function for acetylcholine in a specific thalamocortical pathway.

3. Experiments on non‐pyramidal tract cells have detected a muscarinic depression of some cells, and a nicotinic excitation of some cells above a depth of 600 μ in the cortex.

4. It is suggested that the increased release of acetylcholine from the cortex produced by atropine administration may be due to an excess of muscarinic inhibitory over excitatory synapses in the cortex.