Phosphorus metabolism of intact crab nerve and its relation to the active transport of ions.

Self Cite

(1960) showed that the sodium efflux from cyanide-poisoned squid axons was increased following microinjection of ATP, phosphoenolpyruvate or arginine phosphate. About 0*7 moles of sodium was ejected for each mole of energy-rich phosphate supplied. This figure is considerably lower than that derived for crab nerve and other tissues where the Na: -P ratio is around 3 (for references see Baker, 1965

mentioning

confidence: 71%

A comparison of the phosphorus metabolism of intact squid nerve with that of the isolated axoplasm and sheath.

Baker¹,

Shaw²

1965

Self Cite

“…6B shows that the record was still noisier than those made with a tungsten-halogen light source. The artificial sea water (ASW) sometimes used as the bathing solution was 10 K (Na) ASW (Baker, 1965). The compositions of the isethionate ASW and the chloride ASW used for comparison are given in Table 1.…”

Section: Methodsmentioning

confidence: 99%

Changes in axon light scattering that accompany the action potential: current‐dependent components

Cohen¹,

Keynes²,

Landowne

1972

SUMMARY1. When light scattering was measured during hyperpolarizing and depolarizing voltage-clamp steps, relatively large scattering changes were found during the depolarizing steps. These large changes were found to depend on the time integral of the ionic current and not on the changes in conductance or potential.2. The current-dependent changes were examined at several scattering angles, and three distinct time courses were found. At 30-120, the main change occurred after the current when steps of 2-5 msec duration were used. This change was called I-90. At 15-30°, the change occurred with the same time course as the time integral of the current. This change was called I-25o. At 5-15o the scattering change occurred with a time course intermediate between that of I-90 and I-25o. This change was called I-10o.3. In all experiments, outward potassium and outward sodium currents led to similar light scattering changes indicating that specific effects of the cation carrying the current across the membrane were not involved.4. The size of I-900 was reduced by 29 % when an isethionate artificial sea water was substituted for the normal chloride artificial sea water. This reduction equalled the reduction predicted for a transport number effect at the membrane-solution interface. The time course of I-900 was similar to the predicted time course for a volume change in the periaxonal space, and such volume changes were tentatively identified as the origin of I-90.5. Because of difficulties in measuring the time course of I-25', it was not possible to distinguish between a water of hydration effect and a transport number effect as the cause of this change. Similarly, the origins 728 L. B. COHEN, R. D. KEYNES AND D. LANDOWNE of I-1O' were not identified. Only I-1IO was altered in size and time course when the external refractive index was increased with bovine albumin.6. When the scattering changes during the action potential were examined in light of the voltage-clamp experiments, we concluded that the forward-angle change was potential-dependent and that the long-lasting change at right angles probably represented a swelling of the periaxonal space resulting from the fact that chloride carried a significant fraction of the outward current during the action potential.

“…During activity the inorganic phosphate in the nerve increases (Baker, 1965;Chmouliovsky et al 1969;McDougal & Osborn, 1976), and ATP and CrP are lowered: there is thus no reason to assume that the extra efflux during activity is not mostly released from the inorganic pool.…”

Section: Effect Of Stimulationmentioning

confidence: 99%

“…As a result, ATP is broken down at an increased rate so that its intracellular concentration falls (Greengard & Straub, 1959;Chmou-liovsky, Schorderet & Straub, 1969), the concentration of inorganic phosphate increases (Baker, 1965;Chmouliovsky et al 1969;McDougal & Osborn, 1976), and there is an increase in the heat production and oxygen consumption of the nerve (see Ritchie, 1973). …”

Section: Introductionmentioning

confidence: 99%

Increase in efflux of inorganic phosphate during electrical activity in small non‐myelinated nerve fibres.

Ritchie¹,

Straub²

1978

SUMMARY1. The movements of labelled phosphate were measured in garfish olfactory and in rabbit vagus nerves at rest and during activity.2. In garfish olfactory nerve kept in solutions with 120 mM-sodium and 0-2 mmphosphate the fractional loss of 32p was 9-82 x 10-4 min1. Lowering the sodium concentration of the washing fluid decreased the efflux; lowering the phosphate produced a transient increase with subsequent return towards the efflux in 0-2 mMphosphate. 8. The extra efflux with stimulation seems to result predominantly from an increase in intracellular inorganic phosphate resulting from increased break-down of ATP after activity.