bluuebunny/crossref_metadata_2025 huggingface dataset:
The secretion of calcium and phosphorus into milk.
Authors: Neville M C , Peaker M
Published: December 2014

1. The time course of appearance of radioactivity in milk was studied following close‐arterial infusion of labelled phosphate, Ca or leucine into the mammary artery of lactating goats. Maximum activities were reached at 1.5 hr in all milk fractions including inorganic soluble phosphate, inorganic colloidal phosphate, casein P, soluble Ca, protein‐associated Ca and casein. 2. At 0.5 hr, labelling of the soluble and colloidal phosphate fractions was significantly higher than that of the casein P. 3. Recovery of 32P or 47Ca 3 or more hours after infusion into the cistern of the mammary glands was 98% or greater, indicating that the mammary epithelium is virtually impermeable to [32P]phosphate and 47Ca in the milk to blood direction. 4. Ca and P failed to enter milk in excess of the normal secretion rate when the milk was diluted with isosmotic sucrose given by intraductal injection. 5. These data suggest that milk Ca and phosphate in their various forms are secreted, like protein and lactose, by exocytosis of Golgi vesicles. Unless a paracellular pathway is present, as in oxytocin‐treated animals, the milk concentrations are maintained by virtue of the impermeability of the mammary epithelium to these substances.
Fever induced in rabbits by intravenous injection of bovine serum albumin.
Authors: Hattingh J , Laburn H , Mitchell D
Published: December 2014

1. Bovine serum albumin injected into conscious rabbits produced a dose‐dependent fever of short latency and duration of at least 2 1/2 hr. 2. The fever was not due to contamination by other proteins nor due to contamination by bacterial endotoxin. 3. The fever following albumin injection had characteristics similar to endogenous pyrogen fever. 4. Some traditional ways of distinguishing bacterial endotoxin fever from other types of fever need to be reassessed.
The initiation and maintenance of bradycardia in a diving mammal, the muskrat, Ondatra zibethica.
Authors: Drummond P C , Jones D R
Published: December 2014

1. The cardiac and respiratory responses shown by muskrats in both unrestrained and restrained dives have been compared with responses elicited by stimulation of a number of cardio‐depressant receptor inputs, in an attempt to determine which are most important in initiating and maintaining diving bradycardia. 2. In unrestrained voluntary dives heart rate fell from 310 +/‐ 3 to 54 +/‐ 3 beats min‐1 in 1 to 2 sec, which was significantly below that seen in dives by restrained unanaesthetized or anaesthetized animals. 3. Pouring water on the external nares during maintained artificial ventilation caused heart rate to decline to 76 +/‐ 12 beats min‐1 after 1 sec. Flowing water through the internal nares caused apnoea, in the expiratory position, and bradycardia within one third of a second. Heart rate fell to 20 +/‐ 2 beats min‐1, 1 sec after the start of water flow. Substituting saline for water reduced both the apnoeic and cardiac responses. Bilateral section of the maxillary branch of V and the inferior laryngeal (X) nerves completely abolished the cardiac and respiratory response to water flow. 4. Artificial ventilation throughout periods of nasal stimulation with water or saline reduced the bradycardia, although even the saline driven response could not be completely abolished. Lung deafferentation eliminated any direct effect of artificial ventilation on heart rate during nasal stimulation. 5. Lung deflation caused bradycardia within 0.97 +/‐ 0.17 sec, heart rate falling from 268 +/‐ 7 to 59 +/‐ 4 beats min‐1. Bradycardia also occurred during maintained lung inflation but it was delayed for a period which varied from 6.8 +/‐ 1.8 sec at an inflation pressure of 0.5 kPa to 35 +/‐ 7 sec at 1.5 kPa. 6. Bradycardia caused by nasal water flow or lung deflation was unaffected by bilateral section of the sinus nerve. 7. Artificial ventilation of paralysed muskrats with 5% CO2 in N2 caused bradycardia when Pa, O2 reached 8.4 +/‐ 0.8 kPa and heart rate declined to 76 +/‐ 7 beats min‐1 at 4 kPa. Bilateral section of the sinus nerve delayed bradycardia until Pa, O2 reached 4.5 +/‐ 0.5 kPa. 8. These results suggest that the cardiac response to submergence could be the expression of input from three groups of receptors, nasal, lung and carotid chemoreceptors, although it is not clear how they interact with one another to generate the cardiac responses displayed by unrestrained animals during submergence.
Voltage clamping of unparalysed cut rat diaphragm for study of transmitter release.
Authors: Glavinović M I
Published: December 2014

1. As a result of the cutting procedure there is a decrease in the membrane potential, input resistance, and space constant of the rat diaphragm, and there is no contraction when the phrenic nerve is stimulated. While the reversal potential of end‐plate currents in cut preparations appears normal, the size of miniature end‐plate currents (m.e.p.c.s.) is slightly decreased. 2. An increase in the external concentration of potassium from 2.5 to 10.0 mM results only in a minor change (less than 5%) in statistical parameters of transmitter release (m, n and p). The size of m.e.p.c. is also almost unchanged. 3. A decrease in temperature from 37 degrees to 15 degrees C resulted in a decrease of m, n and p; however, the values are less than 25% smaller at 25 degrees C than at 37 degrees C. The size of m.e.p.c.s is very insensitive to changes in temperature. 4. As previously reported for the frog neuromuscular junction, changes in muscle membrane potential of cut and uncut rat diaphragm due to voltage clamping affect the frequency of m.e.p.c.s only in medium with raised external K concentration. The dependence of frequency of m.e.p.c.s on muscle membrane potential is remarkably similar in cut and uncut preparations. Evoked release in cut preparation in normal medium is not affected by the change in muscle membrane potential.
Endogenous prostaglandins and stimulated gastric secretion in the cat: the effect of various secretory inhibitors.
Authors: Baker R , Jaffe B M , Reed J D , Shaw B , Venables C W
Published: December 2014

1. The effects of cimetidine, somatostatin and atropine upon the outputs of acid, pepsin, prostaglandins (PG) E and F in gastric juice secreted in response to i.v. infusions of pentagastrin and histamine (H) have been studied in the conscious gastric fistula cat. 2. At constant rate infusions secretion of PGE occurs and follows a similar pattern to that of gastric acid. However the ratio of H:PGE varies considerably and to an extent inexplicable in terms of assay variation. 3. Inhibition of acid output is matched by inhibition of the output of PGE, but changes in concentration of PGE suggest this is a volume related phenomenon. 4. It is concluded that gastric juice PGE is most unlikely to have a regulatory effect upon acid secretion.
The velocity of unloaded shortening and its relation to sarcomere length and isometric force in vertebrate muscle fibres.
Authors: Edman K A
Published: December 2014

1. The velocity of shortening at zero load was studied during fused tetanic contractions and single twitches in isolated skeletal muscle fibres of Rana temporaria. 2. The technique used for determination of the speed of unloaded shortening consisted of a series of quick releases of different amplitudes applied at a given instant during activity. The time, delta t, needed for the fibre to take up the slack was plotted against the amplitude of release, delta L. The slope of the straight line relating delta t‐delta L provided a measure of the velocity of shortening at zero load, V0. 3. V0 was compared with force‐velocity data obtained at finite loads (load‐clamp recordings). The predicted velocity of shortening at zero load, derived by hyperbolic extrapolation from velocities at low and intermediate loads, was not significantly different from V0. 4. The temperature dependence of isometric force and of shortening velocity was investigated between 2 and 12 degrees C in the same fibres. Q10 was 2.67 +/‐ 0.07 (S.E. of mean, n = 6) for V0 and 1.24 +/‐ 0.01 for tetanic force. 5. The velocity of unloaded shortening was determined at different sarcomere lengths in the range 1.4‐‐3.1 microns. V0 was constant between 1.65 microns and approximately 2.7 microns. It decreased below 1.65 microns and increased above 2.7 microns. 6. The decrease in velocity at short sarcomere lengths probably reflects an increase of the passive resistance to shortening. The increase in velocity at long sarcomere lengths can be accounted for by the passive compressive force that is produced by the parallel elastic elements of the prestretched fibre. 7. V0 was determined at the peak of the twitch and during the plateau of the fused tetanus in the same fibre. Whereas the peak twitch force varied between 38 and 85% of the tetanic tension in the different fibres (mean: 71 +/‐ 5%, n = 8), V0 during the twitch was 99 +/‐ 2% of the value recorded during the tetanus. Depression of the isometric twitch amplitude to 10% of the control value by dantrolene did not cause any significant reduction of V0.
The responses of afferent fibres from the glabrous skin of the hand during voluntary finger movements in man.
Authors: Hulliger M , Nordh E , Thelin A E , Vallbo A B
Published: December 2014

1. Afferent activity of 111 single units from the glabrous skin area was recorded percutaneously in the median nerve of human subjects, using tungsten electrodes. 2. The majority of the units (103) were classified as low‐threshold mechano‐sensitive units belonging to one of the four categories previously described: rapidly adapting with small receptive fields (RA), rapidly adapting with large receptive fields (PC, presumed Pacinian corpuscle units), slowly adapting with small fields (SA I), and slowly adapting with large fields (SA II). The size of the responses (in number of impulses) to indentation and stretching of the skin was compared with that of the responses elicited during voluntary isotonic finger movements, which avoided trivial excitation of the units by direct touch. 3. All four types of units, and 77% of the single units, were activated by isotonic movements. The decreasing order of responsiveness was PC, SA II, SA I, RA. 4. Almost all responsive units were excited during the dynamic phase of ramp and smooth oscillatory movements. Static responses, on the other hand, occurred only with 50% of the slowly adapting units, corresponding to a third of the total sample (SA II, 81%; SA I, 17%. 5. For all four types of units the dynamic responses to movements were of similar size as the responses to localized skin indentation with a von Frey hair at five times threshold. 6. The results are discussed with regard to the possible implications for kinaesthesia and motor control.
On the separability of two mechanisms involved in the detection of grating patterns in humans.
Authors: Bodis‐Wollner I , Hendley C D
Published: December 2014

1. The detectability of contrast modulation (M) of sinusoidal gratings was explored at the rate of 8 Hz. The luminance profile of a contrast modulated sinusoidal grating is L = L(1 + C cos 2 pi F chi). This stimulus may also be regarded as the sum of a steady grating pattern and counter phase flicker of the same spatial frequency. 2. Contrast modulation sensitivity (1/M) was established in five observers at several levels of constract and over a range of spatial frequencies, where M = delta C/C of delta C is the just detectable contrast change and C is the mean contrast of the grating. The slope of a modulation sensitivity function (C/delta C vs. C) is 1 (i.e. delta C = constant) near threshold contrast at each spatial frequency, but in the suprathreshold contrast range the slope flattens from close to 1 at 1.5 c/deg to almost 0 (delta C/C = constant) at 12 c/deg. 3. Adaptation to a high contrast steady grating of the same spatial frequency as the contrast modulated test gratings shifts each modulation sensitivity function to the right at low contrasts, but not at high. As a result the adapted curves cross their corresponding unadapted ones. At each spatial frequency the modulation sensitivity function is now fitted by a straight line of slope 1. While delta C needs to be higher than half the detection threshold of the same grating at spatial frequencies above 3 c/deg, in the adapted condition the values are nearly equal at each frequency. Thus pattern adaptation unmasks the threshold of the counterphase component of the contrast modulated grating near threshold contrast as well as above it. The phase of the steady adapting grating, relative to the steady component of the test grating, does not make any difference. 4. Apparently contrast modulation reveals differences beyond threshold sensitivity between spatial frequencies adjacent to the peak of the contrast sensitivity curve. For each spatial frequency channel there must be different neural coupling between steady and modulated inputs. Electrophysiological studies using contrast modulated gratings would be useful in the exploration of individual and ensemble properties of neurones of the visual cortex.
Pancreatic acinar cells: the effect of carbon dioxide, ammonium chloride and acetylcholine on intercellular communication
Authors: Iwatsuki N. , Petersen O. H.
Published: December 2014

1. Segments of mouse pancreatic or exorbital lacrimal gland were superfused with saline solutions. Under visual control two micro‐electrodes were inserted into neighbouring cells within the same acinus or into neighbouring acini. Cell to cell electrical coupling was assessed by injecting rectangular current pulses through one electrode and measuring the electrotonic potential change in the same cell (V1) and in the neighbouring cell (V2). Acetylcholine (ACh) was added locally to impaled acini by micro‐ionophoresis from an extracellular micropipette.

2. Exposure of the tissues to a Krebs solution equilibrated with 100% CO2 caused a rapid increase in the size of electrotonic potential changes in the current injection cell and disappearance of the electrotonic potential changes in a neighbouring acinus or cell. This electrical uncoupling of previously coupled cells was rapidly reversible upon return to a solution equilibrated with 95% O2 and 5% CO2.

3. Reduction of electrical intercellular coupling was also obtained using smaller CO2 concentrations (50, 20 or 10%). In these cases the effects developed more slowly and were less dramatic. Reducing the extracellular HCO3 concentration enhanced the uncoupling effect of 10 or 20% CO2. However, weak uncoupling effects were still observed using 10 or 20% CO2 in combination with a high bicarbonate concentration maintaining a constant extracellular pH (7·4).

4. Reductions in extracellular pH (down to 5·5) achieved by varying combinations of Tris base and Tris HCl had no effect on electrical coupling. Brief periods of anoxia (100% N2) also had no effect.

5. Exposure to 20% CO2 markedly enhanced the uncoupling effect of a brief ionophoretic pulse of ACh.

6. Exposure of the tissue to 10 m
M‐NH4Cl, a procedure expected to increase the intracellular pH, counteracted the uncoupling effect of ACh. During sustained uncoupling caused by a sustained ACh stimulation a brief period of exposure to NH4Cl caused an immediate and fully reversible recoupling.

7. It is concluded that variations in intracellular pH have marked effects on the electrical coupling between neighbouring cells in the pancreatic and lacrimal acinar tissue.
Intracellular citrate or externally applied tetraethylammonium ions produce calcium‐dependent action potentials in an insect motoneurone cell body
Authors: Pitman Robert M.
Published: December 2014

1. Electrophysiological observations have been made upon the cell body of an identified motoneurone of the cockroach, Periplaneta americana. Normal responses were compared with those observed after intracellular injection of citrate anions or when the preparation was bathed in solutions containing tetraethylammonium ions (TEA+).

2. Normally when depolarized, the motoneurone soma gave a series of damped oscillations; the amplitude of these responses increased with increase in the applied current.

3. After citrate ions had been injected into the neurone soma, all‐or‐none action potentials were evoked by depolarization; such responses appeared about 5‐10 min after the onset of citrate injection. Injection of EGTA produced similar effects. Citrate and EGTA probably produce their effect through a reduction in the intracellular free calcium concentration.

4. When preparations were bathed in saline solution containing 50 m
M‐TEA+, soma depolarization produced prolonged all‐or‐none action potentials (up to approximately 100 msec duration).

5. The action potentials produced by citrate injection or externally applied TEA+ appeared to have a similar ionic mechanism; they were not depressed by sodium‐free solutions or by tetrodotoxin (4 × 10−6
M) but were reversibly blocked in saline solution containing 40 m
M‐manganous chloride.

6. The overshoot amplitude of action potentials recorded after injection of citrate anions or in solutions containing TEA+ showed a 22·5 mV change for a ten‐fold change in the external calcium concentration.

7. Both intracellular citrate and external TEA+ caused a significant increase in the input resistance and membrane time constant of the motoneurone.

8. It is concluded that action potentials generated under various experimental conditions in the soma of this insect motoneurone map have differing ionic mechanisms.
Inhibition of gamma motoneurone discharge by contraction of the homonymous muscle in the decerebrated cat.
Authors: Ellaway P H , Murphy P R , Trott J R
Published: December 2014

1. The aim of this study has been to determine the autogenetic reflex effects of tendon organ stimulation upon gamma motoneurones in the decerebrated cat. 2. Tendon organs serving a muscle were excited by isometric twitch contractions of some motor units of that muscle. Contractions were elicited by electrical stimulation of the cut peripheral end of part of the ventral root supply, using a stimulus strength at or below maximum for alpha motoneurone axons. Afferent recordings in the same cats as were used to study reflexes of gamma motoneurones showed that tendon organs were powerfully excited during twitch contractions of their muscle. Early discharges were also elicited in both tendon organs and spindle primary afferents. 3. Background discharges of forty‐seven triceps surae gamma motoneurones, ranging in axonal conduction velocity from 17 to 40 m/sec, were recorded from filaments of the muscle nerve. The initial response of twenty‐two (47%) neurones to twitches of the triceps surae was inhibition of their discharge. The latency from time of stimulation of the ventral root ranged from 10 to 22 msec. The lowered probability of firing lasted an average of 25 msec and, occasionally, was seen as a short silent period. 4. The inhibition was reduced in duration by decreasing the resting muscle length so that less active tension was developed during contraction. 5. The inhibition was observed, in one instance, in the spinally transected decerebrated cat. 6. We argue the case that early discharges in tendon organ afferents give rise to the onset of inhibition and that tension dependent discharges of tendon organs contribute further inhibition of gamma motoneurones. 7. Sixteen gamma motoneurones were not affected by contraction but seventeen showed a period of facilitation. The facilitation could occur after a period of inhibition (eight neurones) or as the sole response to contraction. In either case facilitation occurred mainly during relaxation of the muscle and may, in part, be attributable to increased spindle primary ending firing at this time. 8. In discussion a comparision is made of the reflex effects of muscle afferent discharges on alpha and gamma motoneurones.
The function of the sodium pump during differentiation of amphibian embryonic neurones.
Authors: Messenger E A , Warner A E
Published: December 2014

1. A method has been developed for studying the differentiation in tissue culture of ectoderm and mesoderm derivatives, dissected from amphibian embryos which have just completed neurulation. 2. Neurones, striated muscle cells and pigment cells, together with other unidentifiable cell types, differentiated as a monolayer with approximately the same time course as in the whole embryo. The proportion of different cell types in the cultures was measured quantitatively by cell counting. 3. Treatment of embryos during neurulation with the cardiac glycoside strophanthidin reduced the number of neurones which subsequently differentiated in culture. Other cell types were not affected. 4. The relationship between inhibition of neural differentiation and strophanthidin concentration was sigmoid, with maximum inhibition at 10(‐5) M‐strophanthidin and the mid‐point at 5 X 10(‐7) M‐strophanthidin. 35% of neurones differentiating in culture were not affected by glycoside treatment. 5. The glycoside hexahydroscillaren A had no effect on neural differentiation. 6. Increasing extracellular potassium to 100 nM during strophanthidin treatment completely protected differentiating neurones from the inhibitory effect of strophanthidin. 7. Treatment of embryos with 100 mM‐KCl during neurulation had no effect on the subsequent differentiation of neurones. 8. Treatment of cultures with an antibody to mouse salivary gland Nerve Growth Factor reduced the number of neurones by 30%. 9. Exposure to strophanthidin while the embryo moved from the early neural fold stage to the late neural fold stage was as effective in reducing subsequent neural differentiation as treatment throughout neurulation. 10. The proportion of nerve cells in the cultures was not affected if strophanthidin treatment ended before the early neural fold stage or did not begin until the late neural fold stage. 11. Embryos treated with strophanthidin during neurulation and then allowed to grow into tadpoles developed abnormal nervous systems. 10(‐6) M‐strophanthidin had little effect on the volume of grey matter, but reduced the white matter by 50%. 12. The results are consistent with the view that strophanthidin achieves its effect on neural differentiation by inhibiting the sodium pump. They are discussed in the light of the suggestion that activation of the sodium pump is an essential part of nerual differentiation.
Effects of internal potassium and sodium on the anomalous rectification of the starfish egg as examined by internal perfusion.
Authors: Hagiwara S , Yoshii M
Published: December 2014

1. The effects of alterations of the intracellular ionic composition on the properties of anomalous (or inward) rectification of the egg membrane of the starfish, Mediaster aequalis, were studied by using an intracellular perfusion technique. The following results were obtained, analysing the membrane current with the voltage‐clamp technique. 2. The inward rectification of the K conductance depends only on the membrane potential, V, when the K equilibrium potential, VK, is altered by changing the internal K+ concentration at a fixed external K+ concentration, while it depends on V‐VK when VK is altered by changing the external K+ at a fixed internal K+ concentration. 3. From the above the conclusion is reached that the gating of the K channel of the inward rectification depends on V and external but not internal K+ concentration. 4. The conductance of the K channel at a given voltage is roughly proportional to the square root of [K+]i when the latter is altered at a fixed external K+ concentration. 5. Since the conductance is proportional to the square root of [K+]o when this is altered at a fixed internal K+ concentration, the final conclusion is that this conductance is proportional to the geometric mean of the external and internal K+ concentrations. 6. Intracellular Na+ ions are necessary for the activation of inward rectification; the K conductance increases sharply with internal Na+ concentration, reaching saturation at 200 mM. 7. A similar potentiating effect is found for Li+, although it is weaker. Rb+, Cs+ and organic cations such as arginine+ do not have this effect.
Optical probes of membrane potential in heart muscle.
Authors: Morad M , Salama G
Published: December 2014

1. The fluorescent dye Merocyanine‐540 and the two weakly fluoresecnet dyes Merocyanine‐rhodanine and Merocyanine‐oxazolone are shown to respond as optical probes of membrane potential in heart muscle. 2. In frog hearts stained with Merocyanine‐540, the absorption at 540 nm decreases by 0.1‐1.0% and increase at 570 nm excitation wave‐length, the fluorescence increases by 1‐2%. The time course of all three optical measurements follows the kinetics of the action potential. 3. Merocyanine‐rhodanine exhibits potential‐dependent optical responses through a 0.5% decrease in absorption at 750 nm, and Merocyanine‐oxazolone has a 1.0% decrease in absorption at 720 nm. Their optical responses have a signal‐to‐noise ratio of 100/1 and 500/1, respectively. 4. The action spectrum of Merocyanine‐rhodanine is triphasic in frog heart with an increase in transmittance from 780 to 700, a decrease from 700 to 600, and increase from 600 to 450 nm. Merocyanine‐oxazolone shows only increases in transmittance during membrane depolarization. 5. The optical responses of these probes are linear with respect to changes in membrane potential. 6. Pharmacological agents or ionic interventions do not alter the membrane potential sensitivity of Merocyanine‐540. 7. Rapid spectrophotometric measurements at various phases of the action potential indicate that the potential dependent optical signals of Merocyanine‐540 are produced by changes in amplitude of fluorescence and absorption bands. The lack of wave‐length displacement as a function of membrane potential, i.e. electrochromism, is not the mechanism governing the voltage sensitivity of Merocyanine‐540. 8. The data suggest that these Merocyanine dyes bind to the plasma membrane and serve as linear optical probes of membrane potential in heart muscle.
The calcium action potential and a prolonged calcium dependent after‐hyperpolarization in mouse neuroblastoma cells.
Authors: Moolenaar W H , Spector I
Published: December 2014

1. Action potentials elicited in solutions with elevated [Ca2+] (1.8‐40 mM) have been studied in differentiated cells of mouse neuroblastoma clone N1E‐115 in tissue culture. 2. The action potential in high [Ca2+] solutions containing eithr Na+ or Tris is followed by a prolonged after‐hyperpolarization (a.h.p.) lasting 0.5‐4 sec. The a.h.p. reverses sign between ‐75 and ‐85 mV. 3. Externally applied tetraethylammonium (TEA, 15 mM) increases the Ca2+ spike overshoot, prolongs the falling phase and enhances the a.h.p. duration. The a.h.p. is inhibited by Ca2+ antagonists such as La3+, Co2+ and Mn2+. 4. After replacement of Ca2+ by Ba+ or Sr2+ (20mM) action potentials can still be elicited in Na+‐free solution, but no a.h.p. is observed. 5. Increasing [Ca2+] from 1.8 up to 20 mM results in an increased capability of neuroblastoma cells to fire repetitively and in a consistent reduction of the firing rate from about 4‐10 sec‐1 to 0.5‐1.8 sec‐1. 6. It is concluded that Ca2+ entry during the action potential activates a TEA‐resistant K+ conductance which gives rise to the prolonged a.h.p. Data from repetitively firing cells are consistent with the view that the a.h.p. plays a role in the regulation of low‐frequency firing.
Synapse formation in intact innervated cutaneous‐pectoris muscles of the frog following denervation of the opposite muscle
Authors: Rotshenker Shlomo
Published: December 2014

1. Denervation of one cutaneous‐pectoris muscle of the frog induces the formation of new synapses in the intact innervated muscle on the opposite side. After crushing the motor nerve to the left muscle the incidence of polyneuronal innervation in the right intact muscle increased from an average normal value of 16% to an average value of 27% (Rotshenker & McMahan, 1976).

2. The formation of the new synapses in the intact muscle is independent of the presence of denervated muscle fibres or degenerating axons peripheral to the site of axotomy. After removing the left cutaneous‐pectoris muscle, the proportion of polyneuronally innervated muscle fibres in the right intact muscle increased to an average value of 34%.

3. The number of new synapses formed in one muscle is dependent upon the type of the lesion to the motor nerve to the opposite muscle; 40% of the muscle fibres on the right side were found to be polyneuronally innervated after transecting the motor nerve on the opposite side, as compared to 27% after crushing it.

4. The delay with which new synapses are formed on the unoperated side is dependent upon the distance from the spinal cord of the axotomy. New synapses were detected 4‐8 weeks after cutting the opposite nerve close to the muscle. Placing the site of axotomy close to the spinal cord shortened the delay and new synapses were detected as early as 9 days after the operation.

5. The stimulus for the formation of new synapses by an intact nerve is ineffective if the injured nerve on the contralateral side originates from distant segments of the spinal cord. The pattern of innervation in cutaneous‐pectoris muscles was not altered following denervation of distant muscles in the hind limb.

6. These results suggest that the signal for sprouting and synapse formation may arise in the damaged nerve cells, central to the site of axotomy, and then be communicated transneuronally within the spinal cord to the intact motoneurones on the opposite side.
Adenosine receptors in frog sinus venosus: slow inhibitory potentials produced by adenine compounds and acetylcholine.
Authors: Hartzell H C
Published: December 2014

1. Membrane potential changes produced by adenosine and adenine nucleotides, acetylcholine, and vagus nerve stimulation were studied by intracellular recording in the sinus venosus of the frog, Rana pipiens. 2. Acetylcholine (ACh) released from the vagus nerve terminals evoked a slow hyperpolarization lasting several seconds in the cells of the sinus. Ionophoretic application of ACh from a micropipette produced a response which is similar in time course and amplitude to that evoked by vagus nerve stimulation. Bath application of ACh caused a steady hyperpolarization in quiescent preparations, or cessation of action potential generation in spontaneously active preparations. 3. Adenosine and adenine nucleotides produced hyperpolarizations when applied by addition to the bath or by ionophoresis from micropipettes. The hyperpolarization produced by ionophoresis of adenine compounds was somewhat slower than that produced by ACh. 4. Adenosine and the adenine nucleotides, 5'‐AMP, 3'‐AMP, 2'‐AMP, and 5'‐atp were virtually equipotent in their action. Adenosine was at least 1000‐fold more potent than other purine and pyrimidine nucleosides or adenine. Both the ribose and adenine groups were important for agonist activity. 5. The concentrations of agonist required to produce half‐maximal responses were estimated from dose‐‐response curves as 3 x 10(‐7) M for ACh and 2 x 10(‐6) M for ATP. ACh is about 7 times more potent than ATP in producing a hyperpolarization. 6. Adenine compounds act directly upon the cardiac muscle fibres: bath or ionophoretically applied adenine compounds act even when transmitter release from nerve terminals is blocked with high (Mn2+) or when ACh receptors are blocked with atropine. 7. Adenine compounds act on the surface of the muscle fibre membrane. Analogues of adenosine which do not enter the cell are potent agonists of the receptor. An adenyl oligonucleotide too large to enter the cell was 2.6 times more potent per mole than adenosine in producing a hyperpolarization. Drugs such as dipyridamole and 6‐(2‐hydroxy 5‐nitrobenzyl) thioguanosine, which are potent blockers of adenosine transport, potentiate the response of the sinus cells to adenosine. 8. Aminophylline and theophylline are competitive antagonists of adenosine action. The apparent Ki for aminophylline inhibition was 5 microM. 9. The response produced by adenine compounds is partly caused by an increase in the permeability of the membrane to K+. The maximum response to both ACh and adenine nucleotides approached the estimated level of EK or ECl. Replacing extracellular chloride with impermeant isethionate had no effect on responses to ACh or adenine nucleotides. The hyperpolarization was not produced by an activation of an ouabain‐sensitive pump since 20 microM‐ouabain had little effect on the response to adenosine. 10. The response to vagus nerve stimulation is completely blocked by 50 nM‐atropine...
gamma‐Aminobutyric acid efflux from sympathetic glial cells: effect of ‘depolarizing’ agents.
Authors: Bowery N G , Brown D A , Marsh S
Published: December 2014

1. Isolated desheathed rat superior cervical ganglia were incubated in [3H]2,3,‐gamma‐aminobutyric acid ([3H]GABA) solution (1‐‐10 microM for 2‐‐3 hr) in the presence of 10 microM‐amino‐oxyacetic acid (AOAA). The subsequent efflux of tritium into a stream of superfused non‐radioactive GABA‐free Krebs solution at 25 degrees C was measured. 2. In the presence of 10 micrometer‐AOAA the mean basal efflux rate coefficient (k0) for exit of tritium into the superfusion fluid was 0.7 x 10(‐3) min‐1. More than 98% of effluent tritium comprised unchanged [3H]GABA. The rate coefficient showed no correlation with the amount of [3H]GABA previously accumulated by the ganglion. 3. Elevation of [K+]o to greater than 50 mM increased the rate coefficient for [3H]GABA release by up to four times. Changes in efflux rate were not correlated with osmotic changes, and persisted after re‐accumulation of effluent [3H]GABA by the inward carrier was inhibited. The effect of alkali metal cations diminished in the order Rb+ greater than K+ greater than Cs+Li+. Effects of K+ solutions were not reduced by omitting Ca2+ ions, with or without the addition of Mg2+. 4. Application of electrical pulses (0.1‐‐1 msec duration, 1‐‐10 Hz, 4 min trains) to the ganglion soma or to the preganglionic nerve trunk also raised k0. This effect declined with repeated stimulus trains, without an accompanying diminution in the response to K+. Responses to electrical stimulation were not reduced by amethocaine (300 microM), tetrodotoxin (3 microM) or raised [Mg2+i1 (0 mM‐[Ca2+]/30 mM‐[Mg3+]). Separate local superfusion of the pre‐ and post‐ganglionic nerve trunks and of the ganglion soma showed that the response to electrical stimulation was localized to the vicinity of the stimulus and was not propagated along the nerve trunks or across the synapses. 5. Electrical recording from impaled ‘inexcitable’ cells (presumed to be neuroglial cells (Appendix)) indicated that the quantities of K+ ion accumulating during repetitive nerve stimulation are insufficient to stimulate the release of GABA from the glial cells. No physiological role for the release process in modulating neuronal excitability could be adduced.
Effects of acetylcholine on the smooth muscle cell of isolated main coronary artery of the guinea‐pig.
Authors: Kitamura K , Kuriyama H
Published: December 2014

The effects of ACh on the smooth muscle cell membrane and mechanical property of the guinea‐pig main coronary artery were observed by micro‐electrode and isometric tension recording methods. 1. The membrane potential was low (‐‐44 mV) and the membrane was electrically quiescent. Application of outward current pulse generated only a small graded response. The current‐‐voltage relationship was linear for application of inward current pulses. 2. In low external Na or Cl solution the membrane was hyperpolarized. In external K solution of the 1.2‐‐17.8 mM the membrane potential remained nearly the same; however increasing it to more than 29.5 mM depolarized the membrane. The maximum slope of depolarization was 42 mV per tenfold increase in external K. These results indicate that both Na and Cl equilibrium potentials were positive to the resting membrane potential. 3. ACh (greater than 10(‐8) g/ml.) hyperpolarized the membrane, to a maximum of ‐‐67 mV with 10(‐6) g ACh/ml. The dose‐‐response relationship was sigmoidal, and the hyperpolarization was suppressed by atropine (10(‐7) g/ml.). In external K of 1.2‐‐29.5 mM, the application of 10(‐6) g/ml. ACh hyperpolarized the membrane; this ACh‐induced hyperpolarization was maximal in 1.2 mM‐K (from ‐‐42.4 to ‐‐82.4 mV). When the hyperpolarization produced by 10(‐6) g ACh/ml. was plotted against the external K concentration on a log scale, the relationship was linear above 1.2 mM‐K and similar to that observed between the membrane potential and external K concentration between 29.5 and 118 mM in the absence of ACh. However, in a solution containing less than 1.2 mM‐K, the amplitudes of ACh‐induced hyperpolarization were reduced. 4. In Na‐ or Cl‐deficient solution the membrane was hyperpolarized. The peak hyperpolarization to ACh was not modified by these changes in the ionic environments. It is concluded that ACh increases K permeability selectively in this muscle membrane. 5. To observe the reversal potential level of ACh‐induced hyperpolarization, the effects of ACh were observed during the hyperpolarization and subsequent recovery of the membrane on rewarming the tissue following cold storage. When the membrane potential was high (less than ‐‐70 mV) ACh produced depolarization, but when it was low (greater than ‐‐70 mV) ACh produced hyperpolarization. The reversal potential level for ACh‐induced potential change was about ‐‐70 mV. 6. Application of ACh (greater than 10(‐8) g/ml.) evoked a mechanical response. The hyperpolarization of the membrane produced by ACh appeared coincidently with tension development. ACh also enhanced the amplitude of contracture produced by excess external K concentration. 7. It is concluded that ACh might increase K and Ca permeabilities of the membrane and release Ca from the intracellular store, thus causing hyperpolarization of the membrane and contraction.
Calcium carrying system in the giant muscle fibre of the barnacle species, Balanus nubilus
Authors: Beirao P. S. , Lakshminarayanaiah N.
Published: December 2014

1. Single barnacle muscle fibres from Balanus nubilus were internally perfused with an isotonic solution containing 180 m
M‐tetraethylammonium acetate and the effects of Ca concentration in the external solution on the voltage‐clamp currents, especially the initial inward current, were examined.

2. Muscle fibre in external solution containing no added Ca (concentration of Ca < 10−5
M) gave a current—voltage curve that showed a small inward current followed by a small outward current. An identical curve was obtained when the chloride in the external solution was replaced by acetate.

3. The peak inward current increased with increase in Ca concentration in the external solution; but the increase in peak current for equal increments of Ca concentration was reduced and attained saturation conforming to an adsorption regime which can be described by the Langmuir equation.

4. A double reciprocal plot of peak inward current due to Ca as a function of Ca concentration gave values of 20.7 m
M and 200% (the current due to 20 m
M‐Ca normalized to 100%) for the dissociation constant and the maximum current respectively. These values were found to depend on the concentration of Mg used in the external solutions.

5. The peak inward Ca currents measured at two Ca concentrations as a function of pH were unaffected in the pH range 6.5‐8.8; however when the pH was reduced below 6.5, the currents were depressed.
Calcium channels in the high resistivity axonal membrane of photoreceptors of the giant barnacle.
Authors: Edgington D R , Stuart A E
Published: December 2014

1. The distribution of calcium channels in the cell membrane of the photoreceptor neurone of the giant barnacle, Balanus nubilus, was studied by recording intracellularly in or near the soma, in the axon, and near the presynaptic terminals. The membrane properties of these different regions of the cell could be studied by separately superfusing each region with test salines or by cutting the axon between two regions. 2. In the presence of tetraethylammonium (TEA) or 3‐aminopyridine (3‐AP), but not in their absence, Ca dependent action potentials could be evoked with depolarizing current pulses in the somatic, axonal, and terminal regions. Consequently, voltage‐sensitive Ca channels and TEA‐sensitive channels are present in all three regions of the cell. 3. The action potentials recorded from the three regions were similar in their slow times‐to‐peak (30‐300 msec), long durations (0.2‐2 sec in 100 mM‐TEA), and long‐lasting (0.2‐10 sec) undershoots. The action potentials were inhibited by extracellular Co. 4. Clear differences were consistently observed between terminal action potentials and axonal or somatic action potentials in TEA. Terminal action potentials displayed a lower voltage threshold, faster rate of rise, and were less sensitive to inhibition by extracellular cobalt, suggesting that the Ca current is greater in the terminal region. 5. Bathing the receptor axon in low Ca or Co solutions led to a greater attenuation of large depolarizing components of the visual signal as they spread to the presynaptic terminals.
Open‐circuit sodium and chloride fluxes across isolated opercular epithelia from the teleost Fundulus heteroclitus.
Authors: Degnan K J , Zadunaisky J A
Published: December 2014

1. The Na+ and Cl‐ fluxes across opercular epithelia from sea water‐adapted Fundulus heteroclitus were measured in vitro under open‐circuit conditions while bathed on the mucosa with sea water and the serosa with Ringer solution. 2. The mean predicted Na+ flux ratio was 0.94 +/‐ 0.08 and the observed ratio was 1.14 +/‐ 0.12 (n = 15; mean +/‐ S.E. of mean). The difference in these means was not significant (P greater than 0.20). The mean predicted Cl‐ flux ratio was 11.4 +/‐ 0.9 and the mean observed ratio was 1.38 +/‐ 0.27 (n = 10). The difference in these means was significant (P less than 0.001). 3. Ouabain, at 10(‐6) M in the serosal solution, produced a significant (P less than 0.01) reduction in the Na+ efflux while having no significant (P greater than 0.40) effect on the Na+ influx. The agreement between the predicted (1.70 +/‐ 0.14) and observed (1.72 +/‐ 0.18) Na+ flux ratios after ouabain treatment suggested that this effect could be completely attributed to the depolarization of the epithelium secondary to ATPase inhibition. 4. beta‐adrenergic activation by isoprenaline stimulated the Cl‐ efflux 24.2% and alpha‐adrenergic activation by noradrenaline inhibited the Cl‐ efflux 66.5%. These changes occurred oppositely to those predicted by the changes in the electrical gradient produced by these agents, while the changes in the Cl‐ influxes corresponded to the electrical changes. Short‐circuit experiments confirmed these effects on the Cl‐ efflux and the lack of effects on the Cl‐ influx. 5. The results suggested that Na+ was near theromodynamic equilibrium and that the unidirectional fluxes were passive. The effects of alpha‐ and beta‐adrenergic activation suggested that the active Cl‐ secretion may be antagonistically regulated by catecholamines.
Effects of acetylcholine and catecholamines on the smooth muscle cell of the porcine coronary artery.
Authors: Ito Y , Kitamura K , Kuriyama H
Published: December 2014

The effects of acetylcholine (ACh), noradrenaline (NA) and isoprenaline (Isop) on the membrane and mechanical properties of smooth muscle cells of the pig coronary artery were investigated by micro‐electrode, double sucrose gap and isometric tension recording methods. (1) The mean membrane potential was ‐51.4 mV and the membrane was electrically quiescent. Application of outward current pulse generated a graded response. The current‐voltage relationship was linear for application of inward current pulses. The length constant of the tissue was 0.67 mm and time constant of the membrane was 290 msec. The tissue possessed cable‐like properties. (2) ACh (10(‐10) to 10(‐5) g/ml.) did not change the membrane potential and membrane resistance, but NA and Isop hyperpolarized the membrane and reduced the membrane resistance. These actions of catecholamines, presumably mediated by beta‐adrenergic receptors, were suppressed by propranolol but not phentolamine. (3) The minimum depolarization required to produce the contraction was 4 mV by excess extracellular K concentration and 6 mV by electrical displacement of the membrane potential. The amplitude of the contraction evoked by depolarization in excess K was consistently larger than that by the electrical displacement. The minimum concentration required to produce the contraction induced by ACh was 5 x 10(‐9) g/ml. NA and Isop consistently suppressed the contraction evoked by excess extracellular K or by ACh. (4) When the tissue was immersed in Ca‐free EGTA solution containing excess K or Ca‐free EGTA Krebs solution, the time taken for Ca depletion from the intracellular store site was longer with depolarized membranes than that with polarized membranes. ACh evoked contraction, even after the tissue had lost the ability to produce contraction by excess extracellular K in Ca‐free solution. (5) After the tissue had been immersed in Ca‐free solution containing excess K for more than 4 hr, or Ca‐free Krebs solution for more than 2 hr, application of Ca evoked the contraction. These effects of Ca were suppressed by application of catecholamines. The amplitudes of subsequent ACh‐induced contraction in Ca‐free excess K were not suppressed, while there was a suppression of the K‐induced contraction in Ca‐free Krebs solution. (6) It is concluded that the smooth muscle cell of the pig coronary artery possesses muscarinic and beta‐adrenergic receptors. The former mainly activates the mechanical response without affecting the surface membrane while the latter modifies both membrane and mechanical properties.
Time‐ and voltage‐dependent ionic components of the rod response.
Authors: Werblin F S
Published: December 2014

1. The electrical properties of individual rods, physically isolated from the rod network, were measured in terms of the time course of response and voltage‐current relations derived from current steps. Properties were measured in normal and altered bathing media designed to reveal the ionic basis for the time and voltage dependent properties of the rod response. 2. In normal media the rod membrane was strongly outward‐rectifying with slope resistance near 100 M omega when hyperpolarized, but near 10 M omega when depolarized from a typical ambient level near 35 mV. The membrane become inward rectifying for hyperpolarizations beyond ‐95 mV, with slope resistance near 70 M omega. 3. The normal hyperpolarizing overshoot associated with the rod response was strongly potential dependent: the overshoot in response to a current step disappeared when the membrane was first depolarized or hyperpolarized by more than about 10 mV from the ‐35 mV ambient potential level. The decay from overshoot elicited either by current or light, could be approximated with a first order time constant of about 150 msec. 4. In the absence of sodium the peak‐plateau sequence remained intact. Membrane resistance increased during transition to the plateau. The plateau became more hyperpolarized than the early phase during responses beyond ‐75 mV. These results indicate a time‐ and voltage‐dependent conductance other than sodium contributes to the peak‐plateau response, probably potassium. 5. Outward rectification was greatly reduced in the presence of 15 mM‐TEA, suggesting that it is mediated by potassium activation. 6. Inward rectification, and the associated transients near ‐95 mV were eliminated in the presence of 2 mM‐caesium, suggesting that potassium conductance contributes to the time and voltage dependent inward rectification.