Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019829 (Hodgkin's disease)
 30,247 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A number of small organic molecules with general anaesthetic action have been examined for their effects on the voltage-dependent potassium current of the squid giant axon. They include representatives of the three classes of anaesthetics examined in previous studies on the sodium current (Haydon & Urban, 1983a, b, c), i.e. the non-polar molecules n-pentane, cyclopentane and CCl4, several n-alkanols and the inhalation anaesthetics chloroform, halothane, diethyl ether and methoxyflurane. Potassium currents under voltage clamp were recorded in intact and in intracellularly perfused axons before, during and after exposure to the test substances, and the records were fitted with equations similar to those proposed by Hodgkin & Huxley (1952). Shifts in the curves of the steady-state activation against membrane potential and reductions in the potassium conductance at 60 or 70 mV membrane potential have been tabulated. On the same intact axons, all the anaesthetics with the exception of methoxyflurane reduced potassium currents less than sodium currents by about a factor of two or more. For the n-alkanols, butanol to decanol, the concentrations required to reduce the potassium current at 60 mV membrane potential by 50% were determined. For n-butanol to n-heptanol, the standard free energy per CH2 for adsorption to the site of action was estimated to be -2.91 kJ mol-1 as compared with -3.04 kJ mol-1 for reduction of the sodium current. The magnitude of the free energy decreased for alkanols with longer chain lengths. At anaesthetic concentrations that reduce the sodium current by 50%, the hydrophobic substances n-pentane and cyclopentane reduced the maximal sodium conductance, gNa, and the potassium conductance at 70 mV, gK70, equally by about a third, while the n-alkanols reduced both parameters by less than 10%. By contrast, diethyl ether and methoxyflurane were more effective in reducing the maximal potassium conductance. All of the test substances examined, except n-pentane and n-hexane, shifted the voltage dependence of the potassium steady-state activation in the depolarizing direction. A broad qualitative correlation was found between the shifts in the activation curves for sodium and potassium currents but, quantitatively, the agreement between the two shifts was poor. In n-decanol and methoxyflurane solutions, the voltage-clamped potassium currents exhibited pronounced inactivation-like behaviour. These currents can be fitted by the Hodgkin-Huxley formalism if an inactivation term analogous to the sodium current inactivation is added.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The actions of some general anaesthetics on the potassium current of the squid giant axon. 374 76

Ten patients with Hodgkin's disease were examined before and after each administration of vincristine sulfate (2 intravenous injections of 1.4 mg/m2 of body surface during the first week of each month for 3 months). The motor conduction velocity of the peroneal nerve, the conduction velocity in palmar sensory fibres of the median nerve, and the conduction velocity in the H reflex pathway remained unchanged. The amplitude of distal muscle (extensor digitorum brevis) and sensory nerve (median) potentials decreased, while the maximal response of more proximal muscles (soleus) was not significantly modified. The soleus T response quickly decreased, although at the same time the H response was increased in the days following administration of vincristine. Thus the T/H ratio seems to be the only convenient electrophysiological method of evaluating the functional impairment of primary afferent distal segments. These results show that vincristine induces a transitory excitability enhancement of the monosynaptic reflex. It is suggested that the drug may cause an increase in the firing rate in proximal segments of injured Ia fibres. Apart from this phenomenon the electrophysiological results lead to the conclusion that vincristine induces distal axonal degeneration, similar to that in other toxic neuropathies (e.g. acrylamide or n-hexane) where a dying-back process has been clearly demonstrated.
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PMID:Early phase of vincristine neuropathy in man. Electrophysiological evidence for a dying-back phenomenon, with transitory enhancement of spinal transmission of the monosynaptic reflex. 624 89

The effects of the n-alkanes propane to hexane, cyclopropane, cyclopentane and cyclohexane and carbon tetrachloride on the ionic currents and electrical capacity of the squid giant axon membrane have been examined. Both the peak inward and steady-state outward currents were reduced reversibly by each substance, though propane at 1 atm had very little effect. The membrane capacity at 100 kHz was reduced by all substances except propane at 1 atm. Na currents were recorded in intracellularly perfused axons before and during exposure to the hydrocarbons and the records were fitted with equations similar to those proposed by Hodgkin & Huxley (1952). Shifts in the curves of the steady-state activation and inactivation parameters (m infinity and h infinity) against membrane potential, changes in the peak heights of the activation and inactivation time constants (tau m and tau h) and reductions in the maximum Na conductance (gNa) have been tabulated. The effects of the various hydrocarbons and carbon tetrachloride on the parameters of the Hodgkin-Huxley equations suggest that the suppression of the Na current by these substances originates from several different phenomena. The underlying physico-chemical events are considered in the light of the observed capacity changes and of information on artificial pore-containing membranes.
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PMID:The action of hydrocarbons and carbon tetrachloride on the sodium current of the squid giant axon. 687 65