Effects of Na and Ca on the generation and conduction of excitation in the ureter

1965 ◽  
Vol 208 (4) ◽  
pp. 715-719 ◽  
Author(s):  
Makoto Kobayashi
Keyword(s):  
Conduction Velocity ◽  
Renal Pelvis ◽  
Action Potentials ◽  
Conduction Block ◽  
Krebs Solution ◽  
Taenia Coli ◽  
Free Solution ◽  
The Difference ◽  
Conduction Of Excitation ◽  
Normal Ringer

Effects of Na+ and Ca++ on the generation and the conduction of excitation were studied by using a pelvis ureter specimen of cat. Action potentials were recorded simultaneously from the renal pelvis and the various regions of the ureter, and they were used to indicate the arrival of excitation. In Na+-deficient solutions, both the frequency of excitation and the conduction velocity decreased gradually, and finally a conduction block occurred at the border between the renal pelvis and ureter. In Na+-free solution spontaneous excitation was not observed in most cases. When excess Ca++ was added to Na+-free solution, spontaneous excitation was restored, but the concentration of Ca++ necessary for the restoration had to be at least twice that in normal Ringer-Krebs solution. The difference between the ureter and taenia coli was considered with regard to the role that Na+ and Ca++ play in the generation of spontaneous excitation.

The Ionic Basis of Axonal Conduction in the Central Nervous System of Viviparus Contectus (Millet) (Gastropoda: Prosobranchia)

1972 ◽  
Vol 57 (1) ◽  
pp. 41-53
Author(s):  
D. B. SATTELLE
Keyword(s):  
Action Potential ◽  
Conduction Velocity ◽  
Action Potentials ◽  
Slow Component ◽  
Choline Chloride ◽  
Slight Reduction ◽  
Action Current ◽  
Sodium Dependent ◽  
Dependent Mechanism ◽  
Normal Ringer

1. The compound action potential recorded from the pleural-supraintestinal connective of Viviparus contectus consists of a large, slow component with an average conduction velocity of about 0.02 m/sec (at 23° C) and a faster component with a conduction velocity of 0.10 m/sec (at 23° C) for the fastest fibres. 2. Both fast and slow action potentials are rapidly abolished by the substitution of tris chloride and choline chloride for the sodium salts of normal Ringer. Tetrodotoxin, applied at 10-5M rapidly abolishes action potentials in all fibres. It is, therefore, concluded that a largely sodium-dependent mechanism of spike generation operates in all axons of the connective. 3. Lithium ions effectively substitute for sodium ions in maintaining the fast action potentials for extended periods, whereas tetraethylammonium ions do not. 4. When the calcium chloride of normal Ringer is replaced by sucrose, magnesium chloride or barium chloride, conduction of fast action potentials is maintained. A small increase in the sensitivity of all axons to tetrodotoxin is observed in calcium-free Ringer; a slight reduction in the spike amplitude of fast action potentials follows the application of manganous ions at 5 mM/l in normal Ringer. It is concluded that any possible contribution of calcium to the generation of the action current of the fast action potential is very small compared to that of sodium. 5. All axons of the connective function for extended periods in sodium-free (dextran) Ringer. Under these conditions, tetrodotoxin blocks conduction in all fibres at concentrations of 10-6M, suggesting that function in dextran Ringer is maintained by a sodium-dependent mechanism.

Electrophysiology and Ionic Movements in the Central Nervous System of the Snail, Helix Aspersa

1972 ◽  
Vol 57 (2) ◽  
pp. 513-541
Author(s):  
R. B. MORETON
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Helix Aspersa ◽  
Free Solution ◽  
Half Time ◽  
Bathing Medium ◽  
Inward Current ◽  
Sodium Gradient ◽  
The Mean ◽  
Normal Ringer

1. Experiments were carried out on giant neurones in the abdominal ganglia of Helix aspersa in an attempt to determine (a) the relationship between the ionic composition of the extra-neuronal environment and that of the bathing medium, and (b) the identity of the ions responsible for carrying the inward current of the action potential. 2. Potassium ions diffuse readily between the bathing medium and the extraneuronal fluid, the mean half-time for equilibration being 19.2±1.6 sec (S.E.). With the inner connective tissue sheath intact, the mean half-time is increased to 32.8 ± 2.2 sec. Both half-times can be accounted for purely by the geometry of the extra cellular system. 3. Although their effects on the nerve membrane are not quantifiable, it seems likely from the rapidity of their action that other ions, such as sodium, calcium and manganese, are able to move at similar rates between the bathing medium and the surface of the neurones. 4. Repetitive stimulation at frequencies above 2/sec causes a reversible decline in action potential overshoot. The time course of this effect and of the recovery suggests that it is due to depletion of ions in the restricted extracellular space, with subsequent replacement by active transport, and by diffusion from the bathing medium. Some cells also show a hyperpolarization, which is probably due to a change in ionic permeability of the resting cell membrane. 5. Although many cells can give action potentials in sodium-free solution, the overshoot declines gradually over a period of some hours. This decline is reversibly accelerated by 2 mM/l cyanide, but is unaffected by 10-1 M ouabain. But if ouabain is applied in normal Ringer the overshoot declines slowly, and after a time the ability to give action potentials in sodium-free solution is irreversibly lost. 6. Experiments with 10 mM/1 manganous ions gave variable results, some cells being made inexcitable, others little affected; correlation with ability to give action potentials in sodium-free solution was not good. Tetrodotoxin at 10-5 M caused only small reductions in overshoot. 7. It was concluded that the extra-neuronal environment in Helix aspersa is not subject to ionic regulation. The behaviour of the action potential can best be explained by assuming that both sodium and calcium ions contribute to the inward current. The neuronal calcium pump probably resembles the calcium/sodium exchange pump found in squid axons. Under low-sodium conditions, this pump is unable to operate fully, so that the overshoot declines slowly due to loading of the cells with calcium. Poisoning with cyanide accentuates this effect. Ouabain affects only the sodium pump; in sodium-free solution there is no passive sodium influx, so the overshoot is unaffected. In normal Ringer the cells become loaded with sodium, so that subsequent exposure to sodium-free solution reverses the sodium gradient across the cell membrane, counteracting the inward calcium current, and making the cells inexcitable. Restoration of a favourable sodium gradient causes rapid recovery of the action potential in all cases.

The Effects of Sodium-Free Solutions on the Fast Action Potentials of Viviparus Contectus (Millet) (Gastropoda: Prosobranchia)

1973 ◽  
Vol 58 (1) ◽  
pp. 1-14
Author(s):  
D. B. SATTELLE
Keyword(s):  
Conduction Velocity ◽  
Action Potentials ◽  
Excitable Cells ◽  
Normal Pattern ◽  
Sodium Salts ◽  
Weight Losses ◽  
Normal Ringer

1. A 2 h exposure of connectives of Viviparus contectus to sodium-free Ringer, in which dextran maintains osmolarity, results in a decline in the conduction velocity of the fast axons to 50% of the value obtained in normal Ringer. 2. The changes in conduction velocity of the fast axons in response to the replacement in stages of the sodium salts of normal Ringer correspond to those exhibited by conventional excitable cells when tris is the substitute, but depart considerably from this behaviour when dextran is the substitute. 3. Experiments employing mannitol, sucrose, raffinose, inulin and dextran to replace the sodium salts of normal Ringer reveal that dextran alone of these non-electrolytes maintains fast action potentials in the absence of sodium. 4. Weight losses of connectives under sodium-free (isosmotic) conditions are greatest and are most rapidly achieved when dextran (of the range of non-electrolytes studied) replaces the sodium salts of normal Ringer. Adjusting to isotonic conditions (8 mM dextran) does not diminish the ability of this non-electrolyte to maintain fast action potentials. 5. During prolonged perfusion of connectives by tris Ringer brief(5 min) exposures to dextran Ringer at 15 min intervals rapidly restore fast action potentials. The decline of conduction velocity in these restored fibres closely follows the normal pattern of decline when function is maintained continuously in dextran Ringer.

Electronmicroscopic and electrophysiological studies of the teat branch of the XIII thoracic nerve: relationship with lactation in the rat

1988 ◽  
Vol 118 (3) ◽  
pp. 471-483 ◽  
Author(s):  
L. M. Voloschin ◽  
E. Décima ◽  
J. H. Tramezzani
Keyword(s):  
Electrical Stimulation ◽  
Conduction Velocity ◽  
Action Potentials ◽  
Silent Period ◽  
High Amplitude ◽  
Milk Ejection ◽  
Nerve Activity ◽  
Thoracic Nerve ◽  
Myelinated Fibres ◽  
Stimulation Of

ABSTRACT Electrical stimulation of the XIII thoracic nerve (the 'mammary nerve') causes milk ejection and the release of prolactin and other hormones. We have analysed the route of the suckling stimulus at the level of different subgroups of fibres of the teat branch of the XIII thoracic nerve (TBTN), which innervates the nipple and surrounding skin, and assessed the micromorphology of the TBTN in relation to lactation. There were 844 ± 63 and 868 ± 141 (s.e.m.) nerve fibres in the TBTN (85% non-myelinated) in virgin and lactating rats respectively. Non-myelinated fibres were enlarged in lactating rats; the modal value being 0·3–0·4 μm2 for virgin and 0·4–0·5 μm2 for lactating rats (P > 0·001; Kolmogorov–Smirnov test). The modal value for myelinated fibres was 3–6 μm2 in both groups. The compound action potential of the TBTN in response to electrical stimulation showed two early volleys produced by the Aα- and Aδ-subgroups of myelinated fibres (conduction velocity rate of 60 and 14 m/s respectively), and a late third volley originated in non-myelinated fibres ('C') group; conduction velocity rate 1·4 m/s). Before milk ejection the suckling pups caused 'double bursts' of fibre activity in the Aδ fibres of the TBTN. Each 'double burst' consisted of low amplitude action potentials and comprised two multiple discharges (33–37 ms each) separated by a silent period of around 35 ms. The 'double bursts' occurred at a frequency of 3–4/s, were triggered by the stimulation of the nipple and were related to fast cheek movements visible only by watching the pups closely. In contrast, the Aα fibres of the TBTN showed brief bursts of high amplitude potentials before milk ejection. These were triggered by the stimulation of cutaneous receptors during gross slow sucking motions of the pup (jaw movements). Immediately before the triggering of milk ejection the mother was always asleep and a low nerve activity was recorded in the TBTN at this time. When reflex milk ejection occurred, the mother woke and a brisk increase in nerve activity was detected; this decreased when milk ejection was accomplished. In conscious rats the double-burst type of discharges in Aδ fibres was not observed, possibly because this activity cannot be detected by the recording methods currently employed in conscious animals. During milk ejection, action potentials of high amplitude were conveyed in the Aα fibres of the TBTN. During the treading time of the stretch reaction (SR), a brisk increase in activity occurred in larger fibres; during the stretching periods of the SR a burst-type discharge was again observed in slow-conducting afferents; when the pups changed nipple an abrupt increase in activity occurred in larger fibres. In summary, the non-myelinated fibres of the TBTN are increased in diameter during lactation, and the pattern of suckling-evoked nerve activity in myelinated fibres showed that (a) the double burst of Aδ fibres, produced by individual sucks before milk ejection, could be one of the conditions required for the triggering of the reflex, and (b) the nerve activity displayed during milk-ejection action may result, at least in part, from 'non-specific' stimulation of cutaneous receptors. J. Endocr. (1988) 118, 471–483

scholarly journals Conduction velocity of the rabbit facial nerve: a noninvasive functional evaluation

2003 ◽  
Vol 17 (2) ◽  
pp. 126-131 ◽  
Author(s):  
Belmiro Cavalcanti do Egito Vasconcelos ◽  
Cosme Gay Escoda ◽  
Ricardo José de Holanda Vasconcellos ◽  
Riedel Frota Sá Nogueira Neves
Keyword(s):  
Facial Nerve ◽  
Conduction Velocity ◽  
Nerve Conduction ◽  
Action Potentials ◽  
Functional Evaluation ◽  
Surface Electrodes ◽  
Nerve Grafts ◽  
Synthetic Materials ◽  
Facial Nerves ◽  
The Mean

The aim of this study was to evaluate standardized conduction velocity data for uninjured facial nerve and facial nerve repaired with autologous graft nerves and synthetic materials. An evaluation was made measuring the preoperative differences in the facial nerve conduction velocities on either side, and ascertaining the existence of a positive correlation between facial nerve conduction velocity and the number of axons regenerated postoperatively. In 17 rabbits, bilateral facial nerve motor action potentials were recorded pre- and postoperatively. The stimulation surface electrodes were placed on the auricular pavilion (facial nerve trunk) and the recording surface electrodes were placed on the quadratus labii inferior muscle. The facial nerves were isolated, transected and separated 10 mm apart. The gap between the two nerve ends was repaired with autologous nerve grafts and PTFE-e (polytetrafluoroethylene) or collagen tubes. The mean of maximal conduction velocity of the facial nerve was 41.10 m/s. After 15 days no nerve conduction was evoked in the evaluated group. For the period of 2 and 4 months the mean conduction velocity was approximately 50% of the normal value in the subgroups assessed. A significant correlation was observed between the conduction velocity and the number of regenerated axons. Noninvasive functional evaluation with surface electrodes can be useful for stimulating and recording muscle action potentials and for assessing the functional state of the facial nerve.

The Ionic Basis of the Fast Action Potentials in the Isolated CerebroVisceral Connective of Anodonta Cygnea

1969 ◽  
Vol 51 (2) ◽  
pp. 297-318
Author(s):  
ALBERT D. CARLSON ◽  
J. E. TREHERNE
Keyword(s):  
Conduction Velocity ◽  
Action Potentials ◽  
Electrolyte Solutions ◽  
Monovalent Cations ◽  
Bathing Medium ◽  
Anodonta Cygnea ◽  
Sodium Dependent ◽  
Ionic Basis

1. The large axons in the cerebro-visceral connective have been shown to function for appreciable periods in preparations bathed in sodium-free non-electrolyte solutions. 2. The results of experiments on the effects of organic monovalent cations and anions, together with observations on the effects of tetrodotoxin, procaine and manganous ions and the changes in conduction velocity in tris chloride and dextran solutions indicate that the action potentials are, nevertheless, mediated by conventional sodium-dependent mechanisms. 3. Radioisotope experiments show that there is a small fraction, of approx. 0.5 mM/kg. tissue, which does not exchange rapidly with the 22Na in the bathing medium and which can be depleted by stimulation in sodium-free solutions. 4. On the basis of these observations it is suggested that there is sequestered extra-axonal sodium fraction which can be utilized by the large axons to maintain action potentials in preparations bathed in sodium-free solutions.

scholarly journals The Pathology of Tumours of the Urinary Tract

1939 ◽  
Vol 32 (11) ◽  
pp. 1455-1467
Author(s):  
W. D. Newcomb
Keyword(s):  
Urinary Tract ◽  
Connective Tissue ◽  
Renal Pelvis ◽  
Clinical Importance ◽  
Point Of View ◽  
Renal Tubules ◽  
Clear Cut ◽  
Renal Tumours ◽  
The Difference

Attention is called to the difference between the pathologist's and the radiologist's point of view. The reasons for this difference are discussed with special emphasis on renal tumours. Classification of renal tumours. The first main groups are innocent and malignant. Are these really clear-cut or do they blend into one another? The commoner innocent renal tumours are adenoma, fibroma, myoma, lipoma, and angioma. These are rarely of any clinical importance but adenoma is a possible source of hypernephroma. Many elaborate classifications of cancer of the kidney have been proposed but the following four groups are sufficient for most puposes: Carcinoma, hypernephroma, sarcoma, and teratoid tumours. Much the commonest malignant renal tumour in adults is the hypernephroma, thought by Grawitz and others to be derived from ectopic adrenal rests. There is still no agreement concerning their origin but three views are held at the present time: ( a) All are carcinoma of renal tubules. ( b) Some are derived from renal tubules and some from ectopic adrenal. ( c) All are formed from adrenal tissue. These views are discussed with special reference to material in St. Mary's Hospital Museum, and it is suggested that the first view is the most probable although the second cannot be excluded. The teratoid tumours are the commonest in infants and swine. The differences between them and hypernephromata are described. The renal Pelvis, ureter, and bladder all have tumours of the same type and can conveniently be considered together. Connective tissue tumours, both innocent and malignant, are very rare. Papilloma and carcinoma are rare in the pelvis and ureter, but commoner in the bladder. The relation between these two tumours is discussed.

scholarly journals Action Potential Reflection and Failure at Axon Branch Points Cause Stepwise Changes in EPSPs in a Neuron Essential for Learning

2000 ◽  
Vol 83 (3) ◽  
pp. 1693-1700 ◽  
Author(s):  
Stephen A. Baccus ◽  
Brian D. Burrell ◽  
Christie L. Sahley ◽  
Kenneth J. Muller
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Conduction Block ◽  
Neuronal Morphology ◽  
Whole Body ◽  
Reverse Direction ◽  
Mammalian Brain ◽  
Branch Points ◽  
Individual Branch ◽  
Axon Branch

In leech mechanosensory neurons, action potentials reverse direction, or reflect, at central branch points. This process enhances synaptic transmission from individual axon branches by rapidly activating synapses twice, thereby producing facilitation. At the same branch points action potentials may fail to propagate, which can reduce transmission. It is now shown that presynaptic action potential reflection and failure under physiological conditions influence transmission to the same postsynaptic neuron, the S cell. The S cell is an interneuron essential for a form of nonassociative learning, sensitization of the whole body shortening reflex. The P to S synapse has components that appear monosynaptic (termed “direct”) and polysynaptic, both with glutamatergic pharmacology. Reflection at P cell branch points on average doubled transmission to the S cell, whereas action potential failure, or conduction block, at the same branch points decreased it by one-half. Each of two different branch points affected transmission, indicating that the P to S connection is spatially distributed around these branch points. This was confirmed by examining the locations of individual contacts made by the P cell with the S cell and its electrically coupled partner C cells. These results show that presynaptic neuronal morphology produces a range of transmission states at a set of synapses onto a neuron necessary for a form of learning. Reflection and conduction block are activity-dependent and are basic properties of action potential propagation that have been seen in other systems, including axons and dendrites in the mammalian brain. Individual branch points and the distribution of synapses around those branch points can substantially influence neuronal transmission and plasticity.

Transmembrane action potentials and contractions of human atrial muscle

1964 ◽  
Vol 206 (5) ◽  
pp. 1000-1014 ◽  
Author(s):  
William Sleator ◽  
Taisija De Gubareff
Keyword(s):  
Action Potentials ◽  
Krebs Solution ◽  
Duration Of Action ◽  
Atrial Muscle ◽  
Transmembrane Action Potentials ◽  
New Type ◽  
Two Phases ◽  
Low K ◽  
Type Of Behavior ◽  
High Phase

Transmembrane action potentials and contractions were recorded from pieces of human atrial muscle stimulated electrically in Krebs solution. These preparations exhibit a new type of behavior characterized by periodic "cycling" between two phases: high-phase contractions are two to eight times those in low phase, and action potentials have two or more spikes. The phenomenon can occur in a piece of any size, and is most likely at temperatures between 20 C and 33 C. Acetylcholine weakens contractions, reduces duration of action potential (AP) plateau, and usually abolishes double spikes and cycling; this suggests relatively low K+ permeability during the long low plateau. Epinephrine shortens the cycling period and makes low- and high-phase contractions more nearly equal; additional epinephrine leads to bizarre APs and spontaneous activity. This behavior of human atrial tissue reflects intrinsic capabilities of the cell membrane not previously observed in heart. General hypotheses are proposed to account for the double-spiked APs, for cycling, and for relations between the unique contraction patterns and AP configurations.

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