Calcium requirement for axoplasmic transport in mammalian nerve

Ochs, Sidney; Worth, Robert M.; Chan, S. Y.

doi:10.1038/270748a0

Cited by 93 publications

(49 citation statements)

References 14 publications

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“…Alternatively, their presence in the axon could simply reflect the cell's inability to localize channels strictly to certain regions of its membrane, or the channels might subserve some physiological role not directly related to propagation of the visual signal. For example, it has been suggested that intracellular Ca levels might regulate axoplasmic transport (Ochs, Worth & Chan, 1977); perhaps Ca channels are necessary constituents of axonal membranes that maintain or regulate axoplasmic flow through Ca entry caused by depolarization. Voltage-sensitive Ca channels are also found in squid giant axons (Baker, Hodgkin & Ridgway, 1971) and in the axon of the Aplysia R2 giant neurone (Horn, 1977).…”

Section: Resultsmentioning

confidence: 99%

Calcium channels in the high resistivity axonal membrane of photoreceptors of the giant barnacle.

Edgington¹,

Stuart²

1979

The Journal of Physiology

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SUMMARY1. 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 see in 100 mM-TEA), and longlasting (0-2-10 see) 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.

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Section: Resultsmentioning

confidence: 99%

Calcium channels in the high resistivity axonal membrane of photoreceptors of the giant barnacle.

Edgington¹,

Stuart²

1979

The Journal of Physiology

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“…Recently, the requirement of axoplasmic transport for Ca2+ was shown using a desheathed peroneal nerve preparation (Ochs, Worth & Chan, 1977). Transport in vitro was blocked when nerves were incubated in a simple isotonic NaCl or sucrose medium and normal axoplasmic transport was maintained if 5 mM-Ca2+ was added to that simple medium.…”

Section: Introductionmentioning

confidence: 99%

The requirement for calcium ions and the effect of other ions on axoplasmic transport in mammalian nerve.

Chan¹,

Ochs²,

Worth³

1980

The Journal of Physiology

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SUMMARY1. Until recently it was believed that axoplasmic transport in vitro was not affected by Ca2+, transport being normal in Ca2+-free medium. This was found due to the presence of the relatively impermeable perineurial sheath around the nerve trunks. Using a desheathed cat peroneal nerve preparation, axoplasmic transport was shown to require an adequate level of Ca2+ in the external medium. In a buffered Ca2+-free medium, transport began to decline within 30 min and a complete block occurred in 2-6 hr. A concentration of 5 mM-Ca2+ added to a buffered isotonic sucrose or NaCl solution was able to maintain transport. With lower concentrations of Ca2+ of 1 5-3'0 mm, those usually present in the extracellular fluid or in a Ringer medium, some impairment of transport was seen but the addition of 4 mM-K+ restored the normal pattern of axoplasmic transport. With Ca2+ concentrations below 0 75 mm, however, 4 mM-K+ was unable to sustain transport.2. Potassium by itself at a concentration of 4 mm when added to a buffered isotonic sucrose or NaCl medium was unable to prolong the time of transport block beyond that seen in buffered isotonic NaCl or sucrose solutions. In concentrations of K+ up to 25 mm, 1 5-5 mM-Ca2+ was required for normal transport. With moderately higher concentrations of K+ in the range of 50-100 mm, normal appearing transport was seen with or without Ca2+. This was seen whether or not Na+ was present in the medium. At higher levels of K+, 120-150 mm, decreased transport was seen, with or without the addition of either 15 mM-Na+ or Ca2+ in concentrations of 1 5-3-0 mm.3. While Mg2+ could not substitute completely for Ca2+ in maintaining transport, it was able to prolong the time before block occurred. An extra 30-60 min of downflow was seen when 5 mMMg2+ was added to a buffered isotonic NaCl medium. Magnesium also acts synergistically with Ca2+. Concentration of Ca2+ as low as 0-25 mm was, with the addition of 1-5 mM-Mg2+, able to maintain transport.4. The results are interpreted in the light of studies of the mechanism of Ca2+ regulation known to occur in giant nerve fibres and other cells controlling the level of free Ca2+. The relationship of Ca2+ to the mechanism considered to underlie axoplasmic transport in nerve fibres is also discussed.

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“…En el tejido nervioso, por ejemplo, el calcio participa normalmente en funciones como el transporte axonal anterógrado, en el reciclaje de substancias (15)(16)(17) y en la liberación de neurotransmisores de las vesículas sinápticas. Esto último lo realiza despolarizando la membrana presináptica, al desencadenar la liberación exocítica de los neurotransmisores (18).…”

Section: Generalidades Del Calcio En Las Célulasunclassified

ATPasa de calcio en el sistema nervioso

Velandia¹,

Garavito²,

Caldas³

et al. 2001

biomedica

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La bomba de calcio es una proteína integral de la membrana que regula el calcio libre citoplasmático en concentraciones menores de 0,lmM. En la mayoría de las células eucarióticas está ubicada en la membrana, en el plasmalema o en organelos como el reticulo sarcoendoplásmico y los calciosomas. Su actividad está dada por la hidrólisis del ATP, la concentración del ion en el citoplasma y por otros factores que la regulan como la calmodulina, los fosfolípidos y las proteinas-cinasas. Por diferentes métodos, se ha detectado la ATPasa de calcio y su actividad tanto en tejido nervioso central y periférico, como en otros tejidos.Palabras clave: calcio, ATPasa de calcio, citoquímica enzimática, sistema nervioso. Calcium ATPase in the nervous systemThe calcium pump is an integral membrane protein, which regulates free citoplasmatic calcium using ATP energy. It controls citoplasmatic calcium concentrations below 0.lmM. It is located in al 1 eucariotic cells in plasmalemma, sarcoendoplasmic reticulum and calciosomes. Its activity depends on ionic concentration, ATP hydrolysis and other regulators such as calmodulin, phospholipid and protein-kinases.This enzyme and its activity has been detected through several methods in the central nervous system as well as in other tissues.Key words: calcium, calcium ATPase, enzymatic cytochemistry, nervous system En la mayoría de las células, la concentración interna de calcio es de 0,1 mM y la externa de 1 ,O mM (1). Cuando existe un estímulo químico o eléctrico en las células, el calcio ingresa al citoplasma a través de canales, algunos voltajedependientes o activados por ligandos, ubicados sobre la membrana plasmática ( 2 ) . Por propiedades físicas del ion, como su radio atómico y sus cargas positivas, éste se une especí-ficamente a proteínas dependientes de él y desencadena respuestas dentro de la célula, tales como la activación de rutas metabólicas, la liberación de neurotransmisores y la síntesis y activación de proteínas, entre otras. Por estas razones, se considera como un ion mensajero (1-3).Después de su ingreso, la célula regula la concentración del ion, captándolo por medio de Correspondencia: rncaldasa hemagogus.ins.govco Recibido: 07103100; aceptado: 1711 1100 proteínas como la calmodulina, la parvoalbúmina y la troponina C, entre otras (4,5); también puede ser almacenado en organelos especializados o expulsado de la célula. Se conocen dos sistemas a través de los cuales se realiza este último proceso en las células: uno, de intercambio, en el cual se expulsa calcio y entra sodio impulsado por la energía electroquímica generada por el flujo a favor del gradiente de concentración del sodio (2,6); el segundo es un sistema de transporte activo en el que se utiliza la energía liberada por la hidrólisis del ATP para expulsar el ion al espacio extracelular. La proteína que se encarga de esta función se denomina ATPasa de calcio (7,8), la cual actúa con mayor velocidad y afinidad al ion que el sistema de intercambio y que fue descubierta inicialmente en eritrocitos (9,lO).Esta ...

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Calcium requirement for axoplasmic transport in mammalian nerve

Cited by 93 publications

References 14 publications

Calcium channels in the high resistivity axonal membrane of photoreceptors of the giant barnacle.

Calcium channels in the high resistivity axonal membrane of photoreceptors of the giant barnacle.

The requirement for calcium ions and the effect of other ions on axoplasmic transport in mammalian nerve.

ATPasa de calcio en el sistema nervioso

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