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)

1. The effects of 'clinical' concentrations of some general anaesthetics on the minimum stimulus required to produce an action potential in the squid giant axon have been examined as a function of time from exposure to the anaesthetic. The resting potential in these experiments was also monitored. 2. The minimum stimulus varied with time in different ways for different anaesthetics. For chloroform, diethyl ether, n-pentanol, halothane and cyclopropane the stimulus initially declined, reached a minimum after about 3 min and then recovered to near-normal values at 10-15 min. For n-pentane, cyclopentane and, to a lesser extent methoxyflurane, the stimulus often declined to such low values that the axon exhibited spontaneous action potentials which persisted until the anaesthetic was removed. For one substance, the experimental local anaesthetic diheptanoyl phosphatidylcholine, the stimulus increased considerably over the 10-15 min required to reach the steady state. In all instances the axons reverted to normal behaviour after removal of the anaesthetic although the time course by which they did so was more variable than for the initial exposure. 3. For all anaesthetics the resting potential changed in the positive direction monotonically by ca. 1-5 mV and reached a steady state in approximately 3 min. On removal of the anaesthetic the resting potential returned to normal, also monotonically. 4. The voltage-gated Na+ and K+ currents were significantly affected even at the low anaesthetic concentrations used. Estimates of the changes in the Hodgkin-Huxley parameters were obtained partly by direct experiment and partly from results previously obtained for higher anaesthetic concentrations. 5. The time dependencies of the minimum stimuli have been accounted for semi-quantitatively in terms of the resting potential changes and the voltage shifts in the Na+ current steady-state activation, and the time dependencies respectively of these two parameters. 6. Quantitative calculations of the resting potential changes for comparison with experiment have been made based on the changes in K+ conductance determined in the preceding paper (Haydon, Requena & Simon, 1988) and changes in the Hodgkin-Huxley parameters of the Na+ and delayed-rectifier K+ currents. 7. Calculations of the minimum stimulus in the steady state have been made from the experimental resting potential changes and from the anaesthetic-affected Hodgkin-Huxley parameters. Good agreement with the experimental stimuli was found, especially in the prediction of high and low values.
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PMID:Excitation of the squid giant axon by general anaesthetics. 323 44

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

1. Sodium and potassium currents have been recorded in intracellularly perfused squid giant axons before, during and after exposure to solutions of n-pentane in artificial sea water. 2. The currents were fitted with equations similar to those proposed by Hodgkin & Huxley (1952) and the changes in the parameters of these equations in the presence of pentane were calculated. 3. In the range of membrane potential -40 to 40 mV, the time constants for activation (tau m) and inactivation (tau h) of the Na current, and for activation (tau n) of the K current were all reduced by the pentane. 4. The curve of the steady-state inactivation parameter (h infinity) for the Na current against membrane potential was shifted by the pentane in a hyperpolarizing direction (at h infinity = 0.5 this shift was approx. -15 mV in 275 microM-pentane) and the slope at all potentials was reduced. 5. The curve of the steady-state activation parameter (m infinity) for the Na current against membrane potential was also shifted by the pentane in a hyperpolarizing direction (in 153 microM-pentane, 10 mV at m infinity = 0.5). 6. The maximum Na and K conductances gNa and gK were lowered by the pentane, though not usually completely reversibly. 7. The changes in position and slope of the steady-state inactivation curve have been tentatively accounted for in terms of an increase in membrane thickness.
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PMID:Some effects of n-pentane on the sodium and potassium currents of the squid giant axon. 626 68

The "Industrial Heartland" of Alberta is Canada's largest hydrocarbon processing center, with more than 40 major chemical, petrochemical, and oil and gas facilities. Emissions from these industries affect local air quality and human health. This paper characterizes ambient levels of 77 volatile organic compounds (VOCs) in the region using high-precision measurements collected in summer 2010. Remarkably strong enhancements of 43 VOCs were detected, and concentrations in the industrial plumes were often similar to or even higher than levels measured in some of the world's largest cities and industrial regions. For example maximum levels of propene and i-pentane exceeded 100 ppbv, and 1,3-butadiene, a known carcinogen, reached 27 ppbv. Major VOC sources included propene fractionation, diluent separation and bitumen processing. Emissions of the measured VOCs increased the hydroxyl radical reactivity (kOH), a measure of the potential to form downwind ozone, from 3.4 s-1 in background air to 62 s-1 in the most concentrated plumes. The plume value was comparable to polluted megacity values, and acetaldehyde, propene and 1,3-butadiene contributed over half of the plume kOH. Based on a 13-year record (1994-2006) at the county level, the incidence of male hematopoietic cancers (leukemia and non-Hodgkin lymphoma) was higher in communities closest to the Industrial Heartland compared to neighboring counties. While a causal association between these cancers and exposure to industrial emissions cannot be confirmed, this pattern and the elevated VOC levels warrant actions to reduce emissions of known carcinogens, including benzene and 1,3-butadiene.
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PMID:Air quality in the Industrial Heartland of Alberta, Canada and potential impacts on human health. 2568 50