bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations on the action of type A botulinum toxin on frog neuromuscular junctions
Authors: Boroff D. A. , del Castillo J. , Evoy W. H. , Steinhardt R. A.
Published: December 2014

1. Progressive block of neuromuscular transmission in frog sartorius and gastrocnemius preparations by haemagglutinin‐free crystalline Type A botulinum toxin (BTX) was investigated by in vitro application and by injection of the toxin into living animals.

2. Neuromuscular block was characterized by (a) decline in amplitude of evoked twitch contractions, (b) decline in amplitudes of end‐plate potentials (e.p.p.s) and (c) changes in statistical characteristics of spontaneous miniature end‐plate potentials (m.e.p.p.s).

3. Progress of the block was enhanced by nerve stimulation.

4. A decrease in frequency to less than 0·1/sec and decreased average amplitudes of m.e.p.p.s preceded observable impairment of neuromuscular transmission. These changes occurred as early as 3 hr after injection of the toxin into dorsal lymph sacs.

5. The amplitude distributions of m.e.p.p.s changed from a normal distribution to one that showed an increased skewness toward smaller amplitudes as the block progressed. These changes were first detectable as early as 75 min following addition of the toxin to the bath.

6. At later stages of toxin action, e.p.p.s began to decrease in amplitude and eventually failed altogether. E.p.p.s showed a normal quantal variation at very early stages in the block in Mg2+‐treated preparations. At later stages of the block, it was not possible to test the quantal make‐up of the e.p.p.

7. At all stages before complete failure it was possible to obtain normal or greater than normal degrees of synaptic facilitation with paired stimuli to the nerve. This aspect of the coupling of nerve terminal depolarization to transmitter release appears to be relatively unaffected by BTX.

8. Electrical depolarization of nerve terminals in partially blocked preparations evoked a maintained discharge of m.e.p.p.s with an amplitude distribution similar to that of the spontaneous m.e.p.p.s; hyperpolarization of the terminals evokes a distinctly larger class of m.e.p.p.s. In fully blocked preparations, depolarization of the terminals does not evoke transmitter release whereas hyperpolarization continues to yield the larger class of m.e.p.p.s.

9. It is proposed that the neuromuscular block caused by BTX is due to impairment of a process by which vesicles become charged with transmitter before release.
Spontaneous and neurally evoked release of labelled noradrenaline from rabbit olfactory bulbs in vivo
Authors: Brenells Ann B.
Published: December 2014

1. Rabbit olfactory bulbs were labelled with either [3H]noradrenaline (NA) and [14C]urea, or [14C]NA and [3H]inulin. The labelled substances released were collected by a modified cortical cup technique and estimated by liquid scintillation spectrometry.

2. In many experiments only total radioactivity originating from labelled NA was measured. In such cases the term NA radioactivity is used.

3. The spontaneous release of both NA radioactivity and marker radioactivity followed a multiphasic course. After 140 min the rate of efflux of NA radioactivity was significantly slower than that of the labelled marker.

4. Stimulation of one medial olfactory tract, one lateral olfactory tract or the surface of one bulb resulted in a selective increase in release of NA radioactivity. The size of the increase was dependent on the intensity, frequency and duration of stimulation.

5. There was a characteristic delay in the increased release of NA radioactivity following electrical stimulation. Acute lesioning of the olfactory tracts caudal to the stimulating electrode not only abolished this delay, but also resulted in a larger increase in release following stimulation.

6. The radioactivity attributable to unchanged NA was initially 91%, but decreased to 66% after 4½ hr of sample collection. Stimulation did not affect significantly the relative amounts of NA and metabolites released.

7. Replacement of calcium in the Krebs solution by magnesium did not affect measurably the spontaneous release of NA radioactivity. However, after 1 hr; stimulation failed to increase the efflux of NA radioactivity.

8. It is suggested that the results provide further evidence for a role for NA in synaptic transmission in the olfactory bulbs.
Glucose metabolism and lipid mobilization by adipocytes from mice selected for growth
Authors: Mears G. J. , Mendel V. E.
Published: December 2014

1. Experiments were conducted to compare the abilities of epididymal adipocytes from mice selected for growth (line G) and from unselected mice (line C) to: (a) incorporate glucose, (b) respond to insulin, and (c) mobilize lipids, and to relate these abilities to the food intake of the donors.

2. During the 3‐week pre‐experimental period, line G mice gained body weight 78% faster and ate 35% more food than line C mice; both lines had similar intakes per unit of metabolic body size.

3. Line G epididymal fat pads weighed 227% more than those of line C and contained adipocytes which were 38% larger; it was estimated that they contained approximately 65% more cells.

4. The basal rate of glucose incorporated into lipids (per unit protein) was highest in line C adipocytes, whereas the basal rates of glucose oxidation to CO2 and the total glucose incorporation (uptake) were similar for adipocytes from both lines.

5. Insulin (1000 μu./ml.) caused adipocytes from both lines of mice to increase significantly the incorporation of glucose into CO2 and lipids; the largest elevation occurred when the incubation medium contained 0·1 mg glucose/ml. At this concentration of glucose, the minimum effective dose (MED) of insulin to produce a significant increase in glucose oxidation was similar for both lines. However, the MED of insulin necessary to significantly increase glucose incorporation into lipids and into the sum of CO2 and lipids was highest in the larger, line G adipocytes. Furthermore, the magnitude of the insulin‐induced increase in glucose incorporation was much less for line G than for the line C adipocytes.

6. Epinephrine significantly elevated the rates of NEFA and glycerol release and NEFA re‐esterification. The highest rates of NEFA and glycerol release occurred in line C adipocytes, whereas the highest rate of NEFA re‐esterification occurred in the line G adipocytes.

7. Glucose had no effect on NEFA release but significantly elevated the rates of glycerol release (in most instances) and NEFA re‐esterification.

8. The larger number of adipocytes in line‐G adipose tissue allows for more total incorporation of glucose and a greater overall release of glycerol by this tissue. Consequently, a greater reduction of glucose concentration and a larger elevation of glycerol concentration in the blood can occur; either of these could be the feed‐back signal which resulted in the larger long‐term food intake by the line G mice.
The role of arterial chemoreceptors in the breath‐by‐breath augmentation of inspiratory effort in rabbits during airway occlusion or elastic loading
Authors: Callanan D. , Read D. J. C.
Published: December 2014

1. The breath‐by‐breath augmentation of inspiratory effort in the five breaths following airway occlusion or elastic loading was assessed in anaesthetized rabbits from changes of airway pressure, diaphragm e.m.g. and lung volume.

2. When the airway was occluded in animals breathing air, arterial O2 tension fell by 20 mmHg and CO2 tension rose by 7 mmHg within the time of the first five loaded breaths.

3. Inhalation of 100% O2 or carotid denervation markedly reduced the breath‐by‐breath progression but had little or no effect on the responses at the first loaded breath.

4. These results indicate that the breath‐by‐breath augmentation of inspiratory effort following addition of a load is mainly due to asphyxial stimulation of the carotid bodies, rather than to the gradual emergence of a powerful load‐compensating reflex originating in the chest‐wall, as postulated by some workers.

5. The small residual progression seen in animals breathing 100% O2 or following carotid denervation was not eliminated (a) by combining these procedures or (b) by addition of gas to the lungs to prevent the progressive lung deflation which occurred during airway occlusion.

6. Bilateral vagotomy, when combined with carotid denervation, abolished the residual breath‐by‐breath progression of inspiratory effort.
Selective glycogen depletion in skeletal muscle fibres of man following sustained contractions
Authors: Gollnick P. D. , Karlsson J. , Piehl Karin , Saltin B.
Published: December 2014

1. Six healthy males performed sustained contractions with different tensions related to their maximal voluntary contraction (MVC). The isometric exercise consisted of efforts to extend the knee when flexed at an angle of 90°.

2. Biopsy samples were taken from the lateral portion of M. quadriceps femoris before and after different periods (6–45 min) during a series of sustained contractions. Total glycogen content was determined on each muscle sample. In order to evaluate whether the glycogen depletion occurred preferentially in slow twitch (ST) or fast twitch (FT) fibres, serial sections of the muscle samples were stained for myofibrillar ATPase and glycogen (PAS reaction).

3. In all experiments a selective glycogen depletion was observed. At low tensions, the ST fibres and at higher tensions the FT fibres became glycogen depleted. The critical tension at which this conversion in glycogen depletion from ST to FT fibres took place was 20% MVC.

4. It is concluded that at sustained contractions of less than 20% MVC there is a major reliance upon ST fibres and above that level a primary dependence upon FT fibres. It is further suggested that restriction of blood flow and thus availability of oxygen at forces higher than 20% MVC may be the explanation for the present findings.
Crayfish neuromuscular facilitation activated by constant presynaptic action potentials and depolarizing pulses
Authors: Zucker Robert S.
Published: December 2014

1. Experiments were conducted to test the hypothesis that facilitation of transmitter release in response to repetitive stimulation of the exciter motor axon to the crayfish claw opener muscle is due to an increase in the amplitude or duration of the action potential in presynaptic terminals. No consistent changes were found in the nerve terminal potential (n.t.p.) recorded extracellularly at synaptic sites on the surface of muscle fibres.

2. Apparent changes in n.t.p. are attributed to three causes.

(i) Some recordings are shown to be contaminated by non‐specific muscle responses which grow during facilitation.

(ii) Some averaged n.t.p.s exhibit opposite changes in amplitude and duration which suggest a change in the synchrony of presynaptic nerve impulses at different frequencies.

(iii) Some changes in n.t.p. are blocked by γ‐methyl glutamate, an antagonist of the post‐synaptic receptor, which suggests that these changes are caused by small muscle movements.

3. The only change in n.t.p. believed to represent an actual change in the intracellular signal is a reduction in n.t.p. amplitude to the second of two stimuli separated by a brief interval.

4. Tetra‐ethyl ammonium ions increase synaptic transmission about 20% and prolong the n.t.p. about 15%. This result suggests that an increase in n.t.p. large enough to increase transmission by the several hundred per cent occurring during facilitation would be detected.

5. The nerve terminals are electrically excitable, and most synaptic sites have a diphasic or triphasic n.t.p., which suggests that the motor neurone terminals are actively invaded by nerve impulses.

6. When nerve impulses are blocked in tetrodotoxin, depolarization of nerve terminals increases the frequency of miniature excitatory junctional potentials (e.j.p.s), and a phasic e.j.p. can be evoked by large, brief depolarizing pulses. Responses to repetitive or paired depolarizations of constant amplitude and duration exhibit a facilitation similar to that of e.j.p.s evoked by nerve impulses.

7. It is concluded that facilitation in the crayfish claw opener is not due to a change in the presynaptic action potential, but is due to some change at a later step in the depolarization—secretion process.
Characteristics of crayfish neuromuscular facilitation and their calcium dependence
Authors: Zucker Robert S.
Published: December 2014

1. A quantitative description of facilitation in the crayfish claw opener muscle is presented. The facilitation of a test response following one or more conditioning stimuli, and the growth of facilitation during a tetanus, are measured.

2. In superficial central fibres facilitation following one or more impulses can be described as the sum of two components which are both maximum at the end of the conditioning train and decline simultaneously and exponentially with different time constants thereafter.

3. During a tetanus, facilitation to successive stimuli grows more rapidly than is predicted by assuming that each impulse adds a constant facilitative effect to an accumulating total state of facilitation.

4. Sufficiently large values of tetanic facilitation are predicted by a model which assumes that transmitter release is proportional to the nth power of a substance or factor accumulating in nerve terminals. But no single value of n predicts the correct rise of facilitation in a tetanus and the time course of its subsequent decline from the facilitation following a single spike.

5. A model which assumes that the facilitative effects of successive spikes multiply in a tetanus predicts responses that are larger than those observed.

6. The effects of varying the calcium concentration ([Ca2+]) on transmitter release and facilitation were studied. When a magnesium‐EDTA buffering system is used to vary [Ca2+], transmitter release is found to be nearly linearly related to [Ca2+] in the range 0·1–13·5 m
M.

7. The magnitude and time course of facilitation during and following a tetanus are unaffected by varying [Ca2+] between 1·0 and 40 m
M.

8. The relation between ‘steady‐state’ facilitation and stimulus frequency is also unaffected by changing [Ca2+], except that in high [Ca2+] transmitter release appears to saturate at high frequencies (above 30 Hz).

9. The results are discussed in terms of the ‘calcium accumulation’ hypothesis of facilitation. The findings in crayfish appear to be qualitatively consistent with this hypothesis if certain modifications are made in the hypothesis.
Ion fluxes across the pulmonary epithelium and the secretion of lung liquid in the foetal lamb
Authors: Olver R. E. , Strang L. B.
Published: December 2014

1. Experiments were done on exteriorized foetal lambs of 123–144 days gestation to measure bidirectional ion fluxes through the pulmonary epithelium and to compare them with those predicted from the sum of the measured forces determining passive flux according to the Ussing flux‐ratio equation. Fluxes of Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+, Cl−, Br− and I− were measured and permeability constants obtained by following concentrations of their labelled isotopes in lung liquid and plasma after injection into either. Activity ratios were obtained from chemical measurements or tracer distributions, electrical potential differences by placing KCl‐agar bridges, connected to calomel half‐cells, in blood and lung liquid. Lung liquid volume and secretion rate were measured by adding an impermeant tracer (inulin or [125I]albumin) to lung liquid.

2. The permeability sequence of the pulmonary epithelium for alkali metals was, Na+ > K+ > Rb+ > Li+ > Cs+ and that for halides I− ≈ Br− > Cl−. Permeabilities to alkaline earths were lower than for the other ions, no definite sequence being established.

3. There was an electrical potential difference of −1 to −10 mV (mean −4·3 mV) between lung liquid and plasma (lung liquid negative). Plasma/lung liquid chemical activity ratios were less than unity for the halides (Cl−, Br−, I−), and for K+ and Rb+, whereas the ratio of one‐way fluxes (plasma → lung liquid)/(lung liquid → plasma) was in each case greater than unity. From the difference between the measured flux ratios and those predicted from the forces determining passive flux, it was concluded that the halides, K+ and Rb+ were actively transported from plasma to lung liquid, Cl− being quantitatively the most important. Na+ and Ca2+ appeared to move passively down a gradient of electrochemical potential.

4. When alveolar liquid [HCO3−] was artificially raised, a net flux of HCO3− from lung liquid against a gradient of electrochemical activity was observed, suggesting active transport of that ion out of lung liquid.

5. The addition of KCN to lung liquid stopped the secretion of liquid and absorption took place.
Further studies on the role of prostaglandin in fever
Authors: Dey P. K. , Feldberg W. , Gupta K. P. , Milton A. S. , Wendlandt Sabine
Published: December 2014

1. Experiments were carried out in unanaesthetized cats to find out if a prostaglandin is the mediator (a) for the long lasting fever which often follows injections of phsyiological salt solutions into the cerebral ventricles or into the cisterna magna, as well as their perfusions through the cerebral ventricles, and (b) for the sodium fever which occurs during a perfusion of the cerebral ventricles with calcium‐free artificial c.s.f. A fever mediated by prostaglandin should be accompanied by an increase of prostaglandin activity in cisternal c.s.f., and be abolished or prevented by antipyretics like paracetamol or indomethacin which inhibit prostaglandin synthesis. Both criteria were applied.

2. The fever which follows injections or perfusions of physiological salt solutions appears to be mediated by a prostaglandin of the E series, probably E2 (PGE2) because it was accompanied by increased prostaglandin E‐like activity in the c.s.f. and abolished by paracetamol and indomethacin. During the first few days after pre‐treatment of the cats with intramuscular chloramphenicol the injections were rarely followed by fever.

3. The fever which occurs during a perfusion with calcium‐free artificial c.s.f. appears not to be mediated by prostaglandin, because it was not associated with increased prostaglandin activity in the cisternal effluent, and not prevented by paracetamol or indomethacin, although these antipyretics usually attenuated the fever.

4. A perfusion of the cerebral ventricles with artificial c.s.f. containing calcium in an abnormally high concentration (6·25 m
M) brought down fever produced by PGE1, or PGE2, or bacterial pyrogen.
The movement of optically detectable organelles in myelinated axons of Xenopus laevis
Authors: Cooper Paul D. , Smith Richard S.
Published: December 2014

1. Intra‐axonal organelles were detected by darkfield and Nomarski microscopy in isolated myelinated nerve fibres from Xenopus laevis. Nerve fibres from the 8th spinal roots, the sciatic nerve, and identified motor and sensory axons from other hind limb nerves were used. The movement of the organelles was recorded either on motion picture film or by noting the times at which they crossed the lines of an ocular grid.

2. Three groups of organelles were detected in all fibres. A group of particles with round profiles 0·2–0·5 μm in diameter moved somatopetally. Another group of round particles moved somatofugally. The ratio of the number of somatopetally travelling particles to the number of somatofugally travelling particles was about 10:1. The third group of organelles consisted of rod‐shaped bodies about 0·2–0·3 μm in diameter and 1‐8 μm in length; these were usually stationary.

3. All the round particles appeared to move independently of each other with a saltatory motion. The somatopetally and somatofugally travelling particles had statistically different mean velocities of 0·98 and 1·32 μm/sec respectively.

4. Round particles often crossed the node of Ranvier with no appreciable change in velocity. Some, however, were temporarily arrested at the entrance to the node.

5. While the rod‐shaped organelles were usually stationary, they occasionally moved rapidly lengthwise for distances of up to 10 μm. Rarely a rod‐shaped organelle exhibited a continuous saltatory motion.

6. Round particles often travelled in either direction along the edge of rod‐shaped organelles. One rod was observed to move along the path previously taken by a round particle.

7. The findings are discussed with respect to (a) the normality of the preparations, (b) the numbers of particles travelling in each direction, (c) the nature of the organelles, and (d) the mechanisms underlying the motion.

8. We suggest that particles move along microtubules which have specific directionalities and particle affinities. The microtubules are in bundles and are closely associated with rod‐shaped mitochondria.
Secretion and electrogenesis of the supporting cell in the olfactory epithelium
Authors: Okano Masaomi , Takagi Sadayuki F.
Published: December 2014

1. Electrophysiological study disclosed that chloroform and some other odours generate long‐lasting positive potentials in the olfactory epithelium of the bullfrog, while electron microscopical study showed that they elicit vigorous protrusion of the distal cytoplasmic portion of the supporting cell containing the secretory granules.

2. The secretory process of the supporting cell is as follows: The first detectable indication is the protrusion of the apical portion of the supporting cell (Pls. 3 and 4); the protruded part detaches from its maternal supporting cell (Pl. 7 B), floats as a droplet in the mucus (Pl. 5), and finally the secretory granules inside the droplet disintegrate into the mucus (Pls. 6 and 7 A).

3. The secretion was not elicited by the odours which elicit the negative potentials.

4. In Cl−‐free Ringer solution, neither the positive potential nor the protrusion and secretion occurred.

5. When 1‐2 m
M‐Ba2+ in Ringer solution was dripped on the epithelium, both the positive potential and the protrusion and secretion resulted. Subsequent application of chloroform vapour only advanced further disintegration of the secretory granules, but it elicited neither a new protrusion of the granules nor the positive potential.

6. In the olfactory epithelium in which the olfactory cells had degenerated but the supporting cells survived, both the positive potential and the protrusion and secretion occurred, but the negative potential did not.

7. It is concluded that Cl− entry which mainly generates the longlasting positive potential triggers the secretion of the supporting cell.
Cardiac responses to snout immersion in trained dogs
Authors: Gooden B. A. , Stone H. L. , Young S.
Published: December 2014

1. Four dogs were trained to immerse their snout voluntarily for durations up to 30 sec. Indwelling instrumentation was implanted to measure blood flow velocity in the circumflex branch of the left coronary artery, to sample blood from the left atrium and coronary sinus for the determination of PO2, PCO2, pH, oxygen saturation and haemoglobin concentration, and to pace the heart. An index of myocardial oxygen consumption was calculated by multiplying the mean flow velocity by the arteriovenous difference in oxygen content.

2. Mean coronary flow velocity decreased significantly during simulated diving by 26 ± 27% (±
S.D.). The range of decrease in seventeen out of twenty experiments was from −5 to −81%. Heart rate decreased by 48 ± 7% and this bradycardia was abolished by
I.V. atropine.

3. Coronary sinus oxygen saturation increased significantly with snout immersion (three dogs) and arteriovenous difference decreased from 67 ± 10 to 47 ± 5%. The index of myocardial oxygen consumption decreased by 42 ± 19%. This decrease was attenuated slightly by β‐blockade but was abolished by cardiac pacing in three out of four experiments.

4. The present study indicates that the heart consumes oxygen at a considerably reduced rate during simulated diving and therefore plays a direct role in the overall conservation of oxygen. This response appears to result primarily from a negative chronotropic effect induced by increased vagal tone.
Regulation of the cell magnesium in vascular smooth muscle
Authors: Palatý Vladimír
Published: December 2014

1. The relation between [Mg]o and the Mg content of the rat tail artery incubated in Ca‐free solutions was studied.

2. Variation of [Mg]o in Ca‐free Krebs solution between 0·6 and 2·4 m
m did not affect the cell Mg. In ATP‐depleted arteries, a sizeable fraction of the cell Mg was found to be proportional to [Mg]o.

3. An even larger fraction of the cell Mg became proportional to [Mg]o in metabolically active arteries in which the transmembrane gradient of Na had been dissipated as a result of inhibition of the Na pump. In contrast to the extracellular Mg, the fraction responded to a change in [Mg]o at a very slow rate. The size of the fraction was reflected in net uptake of Mg if [Mg]o was higher than 1·2 m
m. The rate of the uptake was lowered markedly by external Ca. All the Mg taken up by the cells was extruded again after restoration of the Na gradient.

4. The uptake of Mg in Ca‐free, ouabain‐containing solution took place even if the concomitant swelling of cells was prevented by substitution of isethionate for external Cl.

5. Under steady‐state conditions and at const. [Mg]o and [Na]o, [Mg]i increased with increasing [Na]i.

6. The results are consistent with the hypothesis that the outwardly directed Mg pump in rat vascular smooth muscle utilizes the energy released in the course of spontaneous influx of Na.
Cells responding to changing image size and disparity in the cortex of the rhesus monkey
Authors: Zeki S. M.
Published: December 2014

1. The cells of the cortex of the posterior bank of the superior temporal sulcus of the monkey appear to be specialized to signal motion in the visual field. In this paper, cells in this cortical area capable of signalling motion towards or away from the animal are described.

2. Two such types of cell were encountered. One type, the opposed movement complex and opposed movement hypercomplex cells, responded to two edges at a given orientation moving towards or away from each other within the receptive fields. These cells were driven either monocularly or binocularly, but when binocularly driven the cells responded in an identical manner to stimulation of each eye, thus suggesting that such cells must receive a double, and opposed, input from each eye. The other type of cell, always binocularly driven, responded to movement in opposite directions on the two retinas, thus suggesting that such cells must receive diametrically opposite connexions from the two eyes.

3. Long penetrations made to study the manner in which such cells were grouped together in the cortex revealed that they were arranged in small groups or clusters, separated from each other by the common directionally selective cells so prominently present in this area. Thus, cells with one type of wiring mechanism were separated from each other by cells receiving another, and more common, type of anatomical wiring.
The internal anal sphincter in the cat: a study of nervous mechanisms affecting tone and reflex activity
Authors: Garrett J. R. , Howard E. R. , Jones W.
Published: December 2014

1. Smooth muscle activities in rectum and internal anal sphincter have been recorded using intraluminal balloons.

2. Reflex activation of the sphincter, caused by distension of the rectum, has been assessed before and after various combinations of blocking drugs.

3. Responses to stimulation of hypogastric or sacral nerves, or to the administration of drugs with autonomic actions have been tested before and after various combinations of blocking drugs.

4. Results indicate that the tone of the internal anal sphincter is influenced by a number of neural mechanisms. These include motor pathways involving both α‐adrenergic and cholinergic mechanisms and inhibitory pathways involving both β‐adrenergic and non‐adrenergic non‐cholinergic mechanisms.

5. Cholinergic contractions of the sphincter were converted to relaxations after α‐adrenergic blockade. This indicates that the contractions are an indirect effect operating through an adrenergic reflex. Cholinergic relaxations may also be indirect and operate through reflex inhibition secondary to rectal contractions.

6. Sphincteric motor activity is controlled largely through α‐adrenergic mechanisms by adrenergic nerves acting directly on the muscle. β‐Adrenergic inhibitory mechanisms are thought to operate indirectly via ganglia.

7. The over‐all control of the sphincter is by complex reflex mechanisms involving numerous pathways and the activity of the sphincter at any one time is determined by the net balance between motor and inhibitory influences.

8. Sacral nerve stimulation indicated that it contains cholinergic nerves to the rectum, non‐adrenergic non‐cholinergic inhibitory axons to the sphincter and variable numbers of adrenergic axons to the sphincter.

9. Responses of the sphincter to drugs and nerve stimulation were often variable, as has been described many times in the literature. It is considered that this is due to complex combinations of indirect reflex effects, secondary to activation of structures outside the sphincter, operating with or against direct effects on the sphincter itself.
On the transmitter function of 5‐hydroxytryptamine at excitatory and inhibitory monosynaptic junctions
Authors: Gerschenfeld H. M. , Tritsch Danièle Paupardin
Published: December 2014

1. Two symmetrical giant neurones located in the cerebral ganglion of Aplysia californica contain 4–6 p‐mole 5‐hydroxytryptamine (5‐HT) and are able to synthesize it (Weinreich, McCaman, McCaman & Vaughn, 1973; Eisenstadt, Goldman, Kandel, Koike, Koester & Schwartz, 1973). Stimulation of each of these neurones evokes excitatory and inhibitory potentials in various cells of the ipsilateral buccal ganglion. In nine buccal neurones it evokes excitatory potentials, in other three, ‘classical’ inhibitory potentials and in one neurone an ‘atypical’ inhibitory potential.

2. The connexion between the giant cerebral neurone and the cells receiving either an excitatory or a ‘classical’ inhibitory input from it are monosynaptic. TEA injection into the cerebral giant neurone, which prolongs the presynaptic spike, causes a gradual increase of both the excitatory and the inhibitory potentials. On the other hand, high Ca2+ media, which block polysynaptic pathways, do not suppress these synaptic potentials.

3. The iontophoretic application of 5‐HT to the buccal neurones receiving excitatory input from the giant cerebral neurones evokes depolarizations showing the pharmacological properties of both A‐ and A′‐responses to 5‐HT (see preceding paper). Antagonists which block only the A‐receptors (curare, 7‐methyltryptamine, LSD 25) block partially the synaptic depolarizing potentials. Bufotenine, which blocks both the A‐ and A′‐receptors, completely blocks the excitatory potentials. Thus, the post‐synaptic membrane of these buccal neurones appears to be endowed with both A‐ and A′‐receptors to 5‐HT.

4. The ‘classical’ inhibitory potentials elicited in three buccal neurones are hyperpolarizations which reverse at — 80 mV and are due to an increase in K+‐conductance. The iontophoretic application of 5‐HT to these post‐synaptic neurones evokes hyperpolarizing B‐responses which are also generated by an increase in K+‐conductance. Antagonists which block the B‐responses (bufotenine, methoxygramine) also block the inhibitory potentials.

5. The ‘atypical’ inhibitory potential evoked in one buccal neurone consists in an hyperpolarization which increases in amplitude with cell hyperpolarization. Iontophoretic application of 5‐HT to this buccal cell evokes an hyperpolarizing β‐response which also increases in amplitude with cell polarization and results from a decrease in both Na+‐ and K+‐ conductances. The monosynaptic character of the ‘atypical’ inhibitory potential is not yet fully proven.

6. It can be concluded that the excitatory and inhibitory synaptic effects evoked in the buccal neurones by the stimulation of the 5‐HT‐containing‐giant cerebral neurones are very likely mediated by 5‐HT.
Evidence on the origin of impulses recorded from dentine in the cat
Authors: Horiuchi H. , Matthews B.
Published: December 2014

1. Recordings have been made from dentine at the tip of the canine teeth of cats using a large Ag/AgCl electrode.

2. All‐or‐none action potentials with complex shapes were recorded when single nerve fibres from the dental pulp were stimulated electrically outside the tooth.

3. The wave forms of these action potentials changed when the stimulation rate was increased from 1/sec to 10/sec, when the temperature of the tooth surface was changed between 17 and 42° C, when the thickness of the dentine was reduced, and when local anaesthetic was applied to the dentine. Only a small, monophasic, positive potential remained after transection of the pulp in the crown of the tooth.

4. The latency of the action potentials was not affected by these same procedures.

5. It is suggested that each wave form represented a compound action potential produced by impulses invading the main branches and terminals of a single nerve in the pulp. Some of the terminals may have penetrated the innermost layers of the dentine.

6. There was no spontaneous discharge from pulpal nerves.

7. A discharge of impulses was recorded from dentine when 2·5 mol/l. NaCl was applied beneath the electrode at the tip of the tooth. By recording simultaneously from dentine and from single fibres from the tooth pulp, it was shown that impulses recorded from dentine were associated with propagated nerve action potentials.
Brown adipose tissue in the new‐born calf (Bos taurus).
Authors: Alexander G , Bennett J W , Gemmell R T
Published: December 2014

1. Electron microscopic examinations revealed that most of the adipose tissue of new‐born calves had the cellular morphology of brown adipose tissue; only subcutaneous tissue had the cellular morphology of white adipose tissue. 2. The cellular morphology of the brown adipose tissue changed progressively to that of white adipose tissue as the age of the calves increased. 3. Infusion of noradrenaline (I.V.) at rates of 1 and 5 mug/kg.min into new‐born calves exposed to a thermoneutral environment increased metabolic rate two‐ to threefold, and also increased rectal temperature and respiration rate. The responses declined as age of calf increased. 4. Approximately 2% of the body weight of new‐born calves appears to be brown adipose tissue.
Excitation and contraction in bovine tracheal smooth muscle.
Authors: Kirkpatrick C T
Published: December 2014

1. The smooth muscle layer of the bovine trachea was studied in vitro with the micro‐electrode and sucrose‐gap techniques. The membrane potential was stable at‐‐47‐6 plus or minus 0–98 (S.E. of mean) mV, and there was no spontaneous electrical or mechanical activity. 2. The cell membrane had strong rectifying properties, making it impossible to elicit action potentials by electrical stimulation in normal Krebs Solution. The rectification was abolished by TEA (30 mmol/l), which depolarized the membrane and produced plateau‐type action potentials. 3. The spontaneous repetitive action potentials produced by TEA were associated with rhythmic oscillatory contractions of the muscle strips. 4. Histamine caused an increased tone, with superimposed rhythmic fluctuations in tension. The electrical response consisted of depolarization, with rhythmic slow oscillations in potential (slow waves) which were synchronous with the fluctuations in tension. 5. Acetylcholine produced smooth, tonic contractures of tracheal muscle strips, and caused simple depolarization of the membrane. No action potentials were recorded. 6. In calcium‐free solutions containing EGTA, the mechanical response to TEA was completely abolished; the response to histamine was greatly reduced; the response to acetylcholine was reduced to a lesser extent. All responses reverted to normal when normal concentrations of extracellular calcium were restored. 7. Lanthanum added to the bathing solution abolished the contraction due to TEA even though the solution contained calcium. It reduced the histamine‐induced contraction to 26% of control, and reduced the acetylcholine‐induced contraction to 58% of control; extracellular calcium was present throughout. 8. It is suggested that TEA produces contraction by promoting influx of calcium ions into the cytoplasm. Acetylcholine, and to a smaller extent histamine, are less dependent upon the presence of extracellular calcium, and may be capable of releasing calcium sequestered within the cell; acetylcholine appears to be more effective in releasing sequestered calcium.
Modification of sodium channel gating in frog myelinated nerve fibres by Centruroides sculpturatus scorpion venom.
Authors: Cahalan M D
Published: December 2014

1. The effect of Centruroides sculpturatus scorpion venom on single frog myelinated nerve fibres was studied. Sodium currents through the nodal membrane were measured under voltage‐clamp conditions before and after exposure to venom in Ringer solution 1‐5 mug/ml. for 1‐3 min. 2. Centruroides venom brings about repetitive firing and increased membrane potential noise. Spontaneous firing was also observed. Eventually the nodal membrane becomes inexcitable following venom treatment. 3. Under voltage clamp with a step depolarization of the membrane potential, activation and inactivation of sodium currents turns on, reaches a peak within about 25 msec, and then declines over several hundred milliseconds. As the amplitude and duration of the depolarizing pulse are increased, the size of the venom‐induced current that follows also increases. 4. The venom‐induced current turns on exponentially with a time constant near the value of the time constant for recovery from inactivation, tau‐h, at the resting membrane potential. A depolarizing pulse inactivates this new current component, while a hyperpolarizing pulse leads to a larger venom‐induced current immediately after the hyperpolarization. Its time course and membrane potential dependence indicate that the venom‐induced current is modulated by the sodium inactivation process. 5. The membrane potential dependence of sodium activation in some channels is shifted by 40–50 mV in the hyperpolarizing direction. Depolarization increases the proportion of channels with shifted activation gating by first‐older kinetics. Following a depolarizing pulse the activation parameter, m‐3, remains elevated for hundreds of milliseconds, allowing channels to reopen as recovery from inactivation occurs. 6. A kinetic model with normal inactivation gating and shifted activation gating in some channels accounts for the observed voltage‐clamp currents and for the repetitive firing evoked by Centruroides venom. In the model normal channels are converted to channels with shifted activation gating by a voltage dependent reaction. 7. The results suggest limits to possible coupling between sodium channel activation and inactivation. Transitions of the inactivation parameter, h, can occur normally in channels with a shifted membrane potential dependence for activation.
The effects of maintained light stimulation on S‐potentials recorded from the retina of a teleost fish.
Authors: Ruddock K H , Svaetichin G
Published: December 2014

1. S‐potential responses to transient and maintained light stimuli have been recorded from units in the mixed rod‐cone retina of a teleost fish species Eugerres plumieri. 2. Four spectral classes of S‐potential were observed, three cone‐ and one rod‐type. The cone‐type responses were subdivided into two L‐type (referred to as L1 and L2), and a C‐type response. Two classes of transient depolarization response were also recorded from those retinal levels associated with the S‐potential responses and these are attributed, tentatively, to rod and cone bipolar activity. 3. L2‐type S‐potentials do not yield constant hyperpolarization during maintained light stimulation, the time course of the response potential, V, being given approximately by (see article) where Vt is the response potential at time t sec following the onset of stimulation, Vo being the initial response potential. In contrast, both hyperpolarizing and depolarizing components of the C‐type response were maintained under conditions of steady illumination. 4. Under maintained light stimulation at saturation illumination level, the rod S‐potentials escape from hyperpolarization in a manner similar to that previously observed for the skate (Dowling & Ripps, 1971). 5. L2‐type responses to transient test stimuli of illumination level I, superimposed on a steady background field of illumination level I', are in some respects consistent with Alpern, Rushton & Torii's (1970) empirical formula (see article) with K, I one‐half and ID constants. However, for the present data, the value of I one‐half is dependent on I'. 6. The significance of Ricco's law for S‐potential responses is discussed in relation to these findings.
The volume and energy content of meals as determinants of gastric emptying.
Authors: Hunt J N , Stubbs D F
Published: December 2014

1. Results were collected from thirty‐three published and unpublished studies of gastric emptying. The volumes of the meals ranged from 50 to 1250 ml., and composition varied from pure carbohydrates to ordinary food. 2. From the published composition of the meals, their nutritive density, as kcal/ml. (4–18 KJ/ml.) was computed: it ranged from zero to 2‐3 kcal/ml. 3. The volume of each meal, or test meal, delivered to the duodenum in 30 min was determined, assuming that gastric emptying was exponential. 4. The greater the nutritive density of a meal, the less was the volume transferred to the duodenum in 30 min. The original volume of meal given was not a determinant of the rate of emptying (ml./min). 5. The slowing of gastric emptying with a meal of high nutritive density was not sufficient to prevent an increased rate of delivery of energy to the duodenum (nutritive density times volume delivered in unit time) with a meal of high nutritive density. 6. Assuming an appropriate relationship for the interaction of a stimulus (kcal/ml.) and duodenal receptors, it was possible to predict a rate of gastric emptying for each meal, given its nutritive density. Knowing the initial volume of the meal, it was possible to predict the mean half time for its emptying. 7. There were eight sets of anomalous results: in four the volumes of meal given were less than 200 ml.; explanations of the anomalies in the other four results could not be provided. 8. The results are consistent with equal slowing of gastric emptying by the duodenal action of the products of digestion of isocaloric amounts of fat, protein and carbohydrate, for example, 4 g fat or 9 g carbohydrate, both 36 kcal, taking carbohydrate and protein as 4 kcal/g and fat as 9 kcal/g.
Effects of noradrenaline infused into the chick hypothalamus on thermoregulation below thermoneutrality.
Authors: Marley E , Stephenson J D
Published: December 2014

1. Hypothermia induced by infusion of noradrenaline into the hypothalamus of 2‐3 week old chicks, within their thermoneutral range, was considerably potentiated by lowering ambient temperature. 2. Noradrenaline‐induced hypothermia was associated with reduced carbon dioxide elimination and reduced blood lactate concentrations whereas leg temperature, electromyographic activity, plasma NEFA and plasma glucose concentrations were increased. 3. Mechanisms postulated to explain the phenomenon are inhibitory and facilitatory effects of noradrenaline on some, but not all, heat production and heat loss mechanisms. Increased electromyographic activity after intrahypothalamic noradrenaline is assumed to be due to lack of effect of noradrenaline on spinal thermosensitive centres; increased plasma NEFA concentration may be due to inhibition of NEFA utilization.
Muscle tension during unrestrained human eye movements.
Authors: Collins C C , O'Meara D , Scott A B
Published: December 2014

1. Tensions in the horizontal rectus muscles have simultaneously and continuously been recorded during unrestricted eye movements in four strabismus patients, using force transducers small enough to be implanted in series between the tendons and their points of insertion on the globe. 2. Levels of tension required to maintain fixation at each position of gaze vary from a minimum of 8–12 g approximately 15 degrees outside of muscle's field of action to a maximum of around 40 g at extreme gaze within the muscle's field of action. When tension is plotted as a function of eye position, the static locus of fixation tension levels exhibits a parabolic relationship. 3. Tensions recorded during smooth following movements parallel or slightly exceed those of fixation. 4. At the onset of a saccade, tension in the agonist rises isometrically, then, as the eye moves, tension levels parallel those of fixation but with an isotonic increment of 15–25 g. At the end of the saccadic movement, tension falls essentially isometrically to the new fixation level. 5. Tension in the antagonist reveals an unexpected peak at the onset of a saccade. 6. For saccadic movements tension increments of 15–25 g above the fixation levels suffice to move the eye rapidly to a new position of gaze, regardless of the duration of the saccade and the location of the new fixation point. 7. Maximum and minimum levels of tension during normal fixation, following and saccadic movements, plotted as a function of eye position, form an operational envelope which defines the limits of muscle forces during normal eye movements. The lowest level of this envelope is the parabolic static locus of fixation tensions.
Biosynthesis of histamine and putrescine in mice during post‐natal development and its hormone dependence.
Authors: Henningsson S , Rosengren E
Published: December 2014

1. Histidine decarboxylase and ornithine decarboxylase activities were determined in mouse kidney and liver during post‐natal development. 2. The content of histamine, putrescine, spermidine and spermine was examined in kidney and liver and in the urine of adult male and female mice. 3. Histamine formation by the kidney was high in both sexes when determined a few days after birth but decreased during weaning. Thereafter, a distinct sex difference was established in that in the female kidney the level of histidine decarboxylase rose several‐fold during adolescence while in the male the level was still further reduced. 4. Putrescine formation by mouse kidney was low in both sexes up to three weeks of age whereafter the amine formation in the male increased conspicuously whereas that of the female kidney remained low. 5. The observed sex differences in tissue enzyme activities were reflected in concomitant differences in the amount of the diamines excreted in the urine. 6. No correlation was found between the actual enzyme levels and the assayed tissue content of histamine, putrescine, spermidine and spermine. 7. Following gonadectomy, the activities of both decarboxylases were significantly altered. Ornithine decarboxylase activity of male kidney and histidine decarboxylase activity of female kidney were strikingly reduced. 8. In the mouse liver, the two decarboxylases displayed no changes comparable with that of the kidney during development.