Articles: anesthetics.
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The aim of the present investigations was to see, if halothane (h), enflurane (e), isoflurane (i), and methoxyflurane (m) exert cytostatic or cytotoxic effects. The experiments were performed on suspension cultures of an established line of Ehrlich ascites tumor cells, which were gased by a mixture of N2 (78%), O2 (20%), and CO2 (2%) to which the volatile anaesthetics in 5 different concentrations were added by vaporizers. Under standardized conditions (incubation time: 24 or 48 hrs; initial cell density: 2 X 10(5) cells/ml culture medium) the following results were obtained: 1. ⋯ With exception of m, which produced a significant decrease of the cellular protein content in the dose range 1.5-2.0 vol% and of the cellular DNA content in all concentrations applied the 3 other anaesthetics caused an increase of the cellular protein content and a somewhat smaller increase of the cellular nucleic acids content. The obtained results indicate that the effect of anaesthetic agents on dividing cells is not due to the same mode or site of action, but to an influence on different stage of the cell cycle, particularly the interphase. Colchicine-like c-mitosis were not obtained.
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A chronic model for investigation of spinal anesthesia in the dog is described. This model incorporates the use of a chronically implanted catheter in the lumbar subarachnoid space. An 18-gauge thin-walled Crawford needle is passes percutaneously into the subarachnoid space. ⋯ Durations of motor blockade were longest for dibucaine and tetracaine, followed in order of decreasing duration by bupivacaine, lidocaine, chloroprocaine, and mepivacaine. The durations of subarachnoid conduction motor blockades in the dog are qualitatively similar to reported values for spinal anesthesia in man. Therefore, the technique described may provide a useful model to evaluate factors that may influence spinal anesthesia.
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Comparative Study
Comparison of the chronotropic responses to local anesthetics (procaine, lidocaine, prilocaine, mepivacaine and bupivacaine) of the canine sinus node in situ.
Effects of local anesthetics (procaine, lidocaine, prilocaine, mepivacaine and bupivacaine) on the sinus node of the nerve-intact dog heart were studied in situ by means of selective perfusion of the sinus node through the sinus node artery. The agents caused a dose-dependent decrease in heart rate and the order of their potency in decreasing the heart rate was as follows, bupivacaine greater than lidocaine=mepivacaine=prilocaine greater than procaine. ⋯ Tetrodotoxin also prevented the positive chronotropic effect of procaine. From these results the following conclusion can be drawn: the negative chronotropic effects of these agents are induced mainly by a direct inhibitory action on the sinus node, and partly by blockade of sympathetic tone, and the interaction with the postganglionic adrenergic nerves plays an important role in the induction of the positive chronotropic responses to procaine and prilocaine.