Comparative efficacy of antiarrhythmic agents in preventing halothane-epinephrine arrhythmias in rats.

Background: Because the relative efficacy of antiarrhythmic agents on halothane-epinephrine arrhythmias has not been well characterized, this study was undertaken to comparatively evaluate the antiarrhythmic action of Na(+)-, K(+)- and Ca(2+)-channel blockers on epinephrine-induced ventricular arrhythmias during halothane anesthesia in rats.

Methods: Rats were anesthetized at random with either halothane (1.5%), isoflurane (2.

Effect of physical exercise on the content of 8-hydroxydeoxyguanosine in nuclear DNA prepared from human lymphocytes.

Effects of exercise on the formation of 8-hydroxydeoxyguanosine (8-OH-dG), a biomarker of oxidative DNA damage, and other purine metabolites such as hypoxanthine, xanthine and uric acid were examined. Venous blood and urine were collected from swimmers and distance runners before and after the usual training. The amount of 8-OH-dG obtained from nuclear DNA of lymphocytes decreased remarkably after intermittent swimming.

Effect of local anaesthetics on the stimulus-secretion coupling in bovine adrenal chromaffin cells.

This study was carried out to determine the relative potencies of local anesthetics to inhibit the cholinergic synaptic transmission using cultured bovine adrenal chromaffin cells, and to clarify if the inhibitory action would correlate with biophysical and pharmacological properties. Local anaesthetics (bupivacaine, etidocaine, tetracaine, lignocaine and procaine; 0.02-2 mM) inhibited carbachol-induced catecholamine release from the cells in a concentration-dependent manner.

Combined effects of adrenergic and intravenous anesthetic agents on inositol monophosphate levels in rat liver prisms.

Combined effects of adrenergic and intravenous anesthetic agents on phosphatidylinositol (PI) turnover were studied using rat liver prisms incubated with [3H]myo-inositol. Rat liver prisms responded to epinephrine, norepinephrine and phenylephrine dose-dependently with an increase in inositol monophosphate (IP1) formation but they did not respond to ephedrine. Dopamine-induced effects were seen only at concentrations as high as 10(-4) mol.

Anesthetic interaction between midazolam and halothane in humans.

The present study was undertaken in humans to determine the anesthetic efficacy of midazolam in terms of its ability to reduce halothane minimum alveolar anesthetic concentration (MAC). Fifty women scheduled for simple or radical hysterectomy were allocated randomly to one of four groups; group A was given no midazolam as a control; groups B, C, and D were given midazolam intravenously by a bolus of 0.1, 0.

Role of imidazoline-preferring receptors in the genesis of epinephrine-induced arrhythmias in halothane-anesthetized dogs.

Background: Drugs with a central alpha 2-adrenergic action can increase the threshold for halothane-epinephrine-induced arrhythmias. Recently, imidazoline-preferring receptors were shown to play a significant role in the hypotensive effect of alpha 2-adrenergic agonists containing an imidazole ring in their structure. To address the question of whether the antiarrhythmic property of the alpha 2-adrenergic agonists was caused by activation of alpha 2-adrenoceptors or imidazoline-preferring receptors in the central nervous system, the effect of an imidazoline (atipamezole) and a nonimidazoline (L-659,066 and yohimbine) alpha 2-adrenergic antagonist were examined as etiologic factors in the genesis of halothane-epinephrine-induced arrhythmias in dogs.

Quantitative analysis of pulmonary clearance of exogenous dopamine after cardiopulmonary bypass in humans.

The contribution of the lung to the clearance of exogenous dopamine after cardiopulmonary bypass (CPB) was analyzed quantitatively in humans and compared with the contribution of the lung before CPB. The pulmonary and arterial plasma concentration of dopamine and the pulmonary plasma flow were measured simultaneously during infusion of dopamine. Contribution of the pulmonary circulation was defined as the ratio between clearance through the pulmonary circulation and the total plasma clearance of dopamine.

Changes in erythrocyte membrane phospholipid composition induced by physical training and physical exercise.

The effects were investigated of physical training and exercise on lipids of the erythrocyte membrane of healthy students. Membrane cholesterol and phospholipids were analysed simultaneously by thin-layer chromatography with a flame ionization detector and the fatty acid composition was determined by gas chromatography. Physically trained students had similar physical characteristics to control students but a significantly higher aerobic capacity, estimated as the maximal oxygen uptake and anaerobic threshold.

Desensitization of junctional and extrajunctional nicotinic ACh receptors expressed in Xenopus oocytes.

Desensitization of nicotinic acetylcholine receptors (AChRs) was studied using the Xenopus oocyte expression system. Mouse and cat extrajunctional AChRs expressed in oocytes desensitized more slowly than Torpedo AChRs. Substitution of the mouse gamma subunit into the Torpedo AChR reduced the rate of desensitization, making it similar to the mouse AChR.

Functional reconstitution of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors from rat brain.

Glutamate receptors belonging to the subclass specifically activated by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) were solubilized from rat forebrain membranes with Triton X-100 and partially purified through a series of three chromatographic steps. Specific [3H]AMPA binding increased 30-60-fold during the isolation procedure. A protein band recognized by antibodies against specific amino acid sequences of the glutamate receptor-A subunit was enriched with each purification step; the molecular mass of this band (105 kDa) corresponded to that of cloned AMPA receptor subunits.

Selective beta 1 and beta 2 adrenoceptor blockade on epinephrine-induced arrhythmias in halothane anaesthetized dogs.

Beta 2 as well as beta 1 adrenoceptors have been recognized in the heart of vertebrates. They mediate a positive chronotropic action of catecholamines. We compared the effect of selective beta 1 and beta 2 adrenoceptor antagonists on the genesis of halothane-epinephrine arrhythmias in dogs.

Tunicamycin increases desensitization of junctional and extrajunctional acetylcholine receptors expressed in Xenopus oocytes by a mechanism independent of N-glycosylation blocking.

Extrajunctional and junctional mouse muscle acetylcholine receptors (AChRs) expressed in Xenopus oocytes in the presence of tunicamycin desensitized more rapidly than the corresponding AChRs synthesized in the absence of tunicamycin. The two types of AChR expressed in non-tunicamycin-treated oocytes could be distinguished by their different rates of desensitization, but tunicamycin diminished this difference. The effect of tunicamycin on the AChR desensitization appeared to be reversible, and coapplication of tunicamycin with acetylcholine (ACh) also caused a similar effect on desensitization of these AChRs suggesting that the effect of tunicamycin was mediated by a mechanism independent of N-glycosylation blocking.

Sequences on the N-terminus of ACh receptor subunits regulate their assembly.

Mutant alpha subunits of Torpedo acetylcholine receptors (AChR) were constructed and expressed in Xenopus oocytes together with other normal subunits to investigate regions in the subunit that are required for subunit assembly. I have found that chimeric alpha subunits, consisting of the N-terminal extracellular domain of the AChR alpha subunit, followed either by the hydrophobic transmembrane segments of GABAA receptor or glutamate receptor subunits, were still recognized as the AChR subunit and associated with co-expressed other normal AChR subunits, suggesting that this part of the N-terminal extracellular domain contains 'assembly signals'.

[A hypertensive crisis during surgery in a patient with neuroblastoma].

Neuroblastoma is the most common solid tumour in infancy and childhood. The tumour usually produces large amounts of catecholamines. Few patients with neuroblastoma, however, were reported to have become hypertensive because of catecholamine metabolism within the tumour itself.

Assembly of mutant subunits of the nicotinic acetylcholine receptor lacking the conserved disulfide loop structure.

Each subunit of the nicotinic acetylcholine receptor (AChR) contains two conserved cysteine residues, which are known to form a disulfide bond, in the N-terminal extracellular domain. The role of this retained structural feature in the biogenesis of the AChR was studied by expressing site-directed mutant alpha and beta subunits together with other normal subunits from Torpedo californica AChR in Xenopus oocytes. Mutation of the cysteines at position 128 or 142 in the alpha subunit, or in the beta subunit, did not prevent subunit assembly.

Enhancement by propofol of epinephrine-induced arrhythmias in dogs.

Although propofol is a widely used intravenous anesthetic, its effect on epinephrine-induced arrhythmias remains unknown. This study examined the possible interaction between propofol and epinephrine that might affect the induction of ventricular arrhythmias in dogs. The arrhythmogenic threshold of epinephrine was determined during anesthesia with halothane alone, propofol alone, etomidate alone, or etomidate plus varying doses of propofol.

Phenytoin prevents epinephrine-induced arrhythmias through central nervous system in halothane-anesthetized dogs.

The authors investigated the effect of phenytoin through the central nervous system on epinephrine-induced arrhythmias in halothane-anesthetized dogs. The arrhythmogenic dose (AD) of epinephrine during halothane anesthesia was determined in the presence of phenytoin (1 mg/kg), vehicle, and saline, which were administered directly into the cisterna magna. Phenytoin increased the AD of epinephrine as compared with vehicle or saline.

Site-directed mutagenesis of the conserved N-glycosylation site on the nicotinic acetylcholine receptor subunits.

The role of the conserved N-glycosylation site on each subunit of the Torpedo acetylcholine receptor (AChR) in the biogenesis and function of the receptor was examined by expressing site-directed mutant subunits in Xenopus oocytes. Different mutant subunits caused different effects. The most striking effect was seen with the mutant gamma subunit which, when co-expressed with alpha, beta, and delta subunits, caused degradation of all the subunits.

Dexmedetomidine prevents epinephrine-induced arrhythmias through stimulation of central alpha 2 adrenoceptors in halothane-anesthetized dogs.

Since alpha 2-adrenergic agonists have important effects on the adrenergic system that have recently been applied to the anesthetic setting, we investigated the effect of stimulation of alpha 2 adrenoceptors on epinephrine-induced arrhythmias in halothane-anesthetized dogs. The arrhythmogenic threshold for epinephrine was determined during halothane anesthesia in the presence of dexmedetomidine, a selective alpha 2 agonist, and L-medetomidine, a stereoisomer of medetomidine that lacks alpha 2-agonist activity. Dexmedetomidine increased the arrhythmogenic threshold for epinephrine in a dose-dependent manner during halothane anesthesia.

Contribution of the lungs to the clearance of exogenous dopamine in humans.

The contribution of the lungs to the clearance of exogenous dopamine was analyzed in humans by measuring plasma pulmonary concentrations of dopamine and the pulmonary plasma flow before and after infusion of dopamine. Contribution of the lungs was defined as the ratio between clearance by the lungs and the total plasma clearance of dopamine. Significant transpulmonary gradient of plasma dopamine was observed with infusions at rates of 1.

Pentazocine-induced catecholamine efflux from the dog perfused adrenals.

This study has been undertaken to determine whether pentazocine induces catecholamine efflux from the adrenal medulla as a mechanism for its sympathomimetic effect. Dog isolated adrenals were perfused retrogradely with modified Locke's solution. The efflux of catecholamines from dog perfused adrenals was increased from the resting output of 0.

Roles of beta 1- and beta 2-adrenoceptors in the mechanism of halothane myocardial sensitization in dogs.

The authors investigated the comparative roles of beta 1- and beta 2-adrenoceptors in myocardial sensitization by halothane in dogs. The arrhythmogenic dose (AD) of isoproterenol was determined in the presence of various doses of phenylephrine during halothane anesthesia in dogs, and the influences of 1-metoprolol (beta 1-antagonist) and ICI-118,551 (beta 2-antagonist) on the AD were examined. In the presence of 1-metoprolol, the AD of isoproterenol was significantly greater than the control, but in the presence of ICI-118,551, the AD of isoproterenol was lower.

Myocardial epinephrine sensitization with subanesthetic concentrations of halothane in dogs.

The authors investigated myocardial epinephrine sensitization by subanesthetic concentrations of halothane. The dose-response relationship for the action of halothane was examined with etomidate plus varying subanesthetic concentrations of halothane in dogs. The arrhythmogenic threshold of epinephrine was decreased in a dose-dependent manner at end-tidal concentrations of halothane between 0.

Antibiotics cause changes in the desensitization of ACh receptors expressed in Xenopus oocytes.

ACh receptors (AChRs) synthesized in Xenopus oocytes which were cultured in medium containing gentamicin desensitized much more rapidly than those expressed in the absence of gentamicin. The effect caused by 24 h incubation in gentamicin could not be reversed by leaving oocytes in culture medium without gentamicin for 24 h. In addition, gentamicin exhibited a direct reversible blocking action on the function of AChRs.