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Bioorganic & Medicinal Chemistry Jul 1999Endovesiculation by large unilamellar vesicles (LUVs) induced by cationic amphiphiles is described in this work. A recent procedure to monitor phagocytosis of vesicles...
Endovesiculation by large unilamellar vesicles (LUVs) induced by cationic amphiphiles is described in this work. A recent procedure to monitor phagocytosis of vesicles by macrophages by determining the amount of the simultaneously internalized water_soluble fluorescent dye HPTS with external quencher was adapted to LUVs (Daleke, D. L.; Hong, K.; Papahadjopoulos, D. Biochim. Biophys. Acta 1990, 1024, 352). Compared to dibucaine and safingol, the local anesthetic chlorpromazine (CPZ) was found to be the most efficient inducer of HPTS-internalization by LUVs. Control experiments using LUVs with entrapped HPTS indicated that the observed dye-internalization does not originate from transient lysis. A strong increase in activity above the critical micelle concentration of CPZ implies the importance of CPZ-micelles for endovesiculation. The significantly less efficient CPZ-induced HPTS-internalization by LUVs with 68 nm compared to 176 nm diameter further diminishes the likelihood of a micelle/bilayer fusion mechanism and supports the presence of 'zipper-type' endovesiculation by LUVs with diameters as small as 68 nm.
Topics: Arylsulfonates; Chlorpromazine; Dibucaine; Dose-Response Relationship, Drug; Endocytosis; Fluorescent Dyes; Liposomes; Phosphatidylcholines; Pyridinium Compounds; Spectrum Analysis; Sphingosine
PubMed: 10465411
DOI: 10.1016/s0968-0896(99)00076-0 -
Anaesthesia Nov 1998A fit 36-year-old parturient received a general anaesthetic for manual removal of a retained placenta. She underwent rapid sequence induction of anaesthesia with...
A fit 36-year-old parturient received a general anaesthetic for manual removal of a retained placenta. She underwent rapid sequence induction of anaesthesia with suxamethonium, shortly followed by 10 mg of mivacurium. One hour later she had failed to establish adequate ventilation despite administration of drugs to reverse neuromuscular blockade. A provisional diagnosis of suxamethonium-related apnoea was made and her lungs were ventilated overnight on the Intensive Care Unit. Plasma cholinesterase levels at the time were reduced to one-third of normal, with normal dibucaine and fluoride numbers. One month later her levels were back within the reference range.
Topics: Adult; Apnea; Cholinesterases; Female; Humans; Isoquinolines; Mivacurium; Neuromuscular Depolarizing Agents; Neuromuscular Nondepolarizing Agents; Postpartum Period; Pregnancy; Succinylcholine
PubMed: 10023281
DOI: 10.1046/j.1365-2044.1998.00581.x -
Methods and Findings in Experimental... 1998Compound action potentials (CAP) in response to orthodromic stimulation of the presynaptic nerve trunk were recorded extracellularly from the bullfrog sympathetic... (Comparative Study)
Comparative Study
Compound action potentials (CAP) in response to orthodromic stimulation of the presynaptic nerve trunk were recorded extracellularly from the bullfrog sympathetic ganglion. Application of lidocaine, tetracaine or dibucaine significantly suppressed the amplitude of CAP. In the presence of phorbol 12,13-dibutyrate (PDBu), an activator of protein kinase C, lidocaine suppression was 3.5-fold more potent, but suppressive effects of tetracaine and dibucaine were not potentiated by PDBu. The acetylcholine (ACh)-induced depolarizing response intracellularly recorded from sympathetic ganglion cells was markedly suppressed by PDBu. Thus, activation of protein kinase C augmented the transmitter release by phosphorylating certain proteins involved in the release mechanism at presynaptic nerve terminals, while it suppressed the nicotinic ACh-receptor activity by phosphorylation at the postsynaptic membrane. However, activation of protein kinase C apparently facilitates synaptic transmission because the augmentation of transmitter release was larger than the suppressive effect on the nicotinic receptors. From these results, it seems likely that protein kinase C activation was responsible for the modified action of lidocaine although the mechanism of this effect is unclear.
Topics: Anesthetics, Local; Animals; Dibucaine; Ganglia, Sympathetic; Lidocaine; Patch-Clamp Techniques; Phorbol 12,13-Dibutyrate; Ranidae; Synaptic Transmission; Tetracaine
PubMed: 9789872
DOI: 10.1358/mf.1998.20.6.485711 -
Pharmacology, Biochemistry, and Behavior Feb 1998Intravenous (I.V.) cocaine (0.03-3 mg/kg) produced dose-dependent, rapid, and brief increases in blood pressure (BP) in conscious rats pretreated with the dopamine...
Intravenous (I.V.) cocaine (0.03-3 mg/kg) produced dose-dependent, rapid, and brief increases in blood pressure (BP) in conscious rats pretreated with the dopamine receptor antagonist, SCH 23390. Monoamine uptake inhibitors structurally analogous to cocaine (cocaethylene, CFT, betaCIT, CPT, (+)-cocaine, norcocaine, and benztropine) also produced this rapid pressor response, whereas structurally unrelated uptake inhibitors with diverse monoamine transporter selectivities (BTCP, indatraline, GBR 12935, mazindol, nomifensine, and zimeldine) either did not produce a rapid pressor response or produced only a small pressor response. At nonconvulsant doses, the sodium channel blockers acetylprocainamide, dibucaine, dyclonine, prilocaine, proparacaine, quinidine, and tetracaine produced a small pressor response or no increase in BP. In rats implanted with telemetric devices, cocaine and its analog, CFT, produced a biphasic pharmacological response that consisted of an initial brief and abrupt behavioral arousal associated with a rapid, large increase in BP followed by prolonged, parallel increases in BP and locomotor activity. Pretreatment with SCH 23390 prevented the prolonged but not the initial rapid and brief pressor and activity responses to both cocaine and CFT administration. The present data suggest that the inhibition of dopamine, norepinephrine, or serotonin transporter functions, either alone or in combination, does not mediate the rapid pressor response to cocaine. The sodium channel-blocking action of cocaine per se does not appear to be involved in the rapid pressor response to cocaine. Finally, the present results confirm previous findings that dopaminergic mechanisms mediate the prolonged increases in BP and locomotor activity produced by cocaine.
Topics: Animals; Biogenic Monoamines; Blood Pressure; Carrier Proteins; Cocaine; Dose-Response Relationship, Drug; Male; Motor Activity; Neurotransmitter Uptake Inhibitors; Rats; Rats, Sprague-Dawley; Sodium Channels; Telemetry
PubMed: 9476974
DOI: 10.1016/s0091-3057(97)00448-6 -
British Journal of Pharmacology Nov 19971. Glutamate receptor activation has been previously shown to result in mitochondrial depolarization and activation of the mitochondrial permeability transition pore in...
1. Glutamate receptor activation has been previously shown to result in mitochondrial depolarization and activation of the mitochondrial permeability transition pore in cultured neurones. In this study, we characterized the effects of two putative permeability transition inhibitors, namely trifluoperazine and dibucaine, on mitochondrial depolarization in rat intact, cultured forebrain neurones. 2. Permeability transition was monitored by following mitochondrial depolarization in neurones loaded with the mitochondrial membrane potential-sensitive fluorescent indicator, JC-1. Trifluoperazine (10 20 microM) and dibucaine (50-100 microM) inhibited or delayed the onset of glutamate-induced permeability transition. 3. We also investigated the effects of trifluoperazine and dibucaine on neuronal recovery from glutamate-induced Ca2+ loads. Trifluoperazine affected Ca2+ recovery in a manner similar to the mitochondrial Na+/Ca2+ exchange inhibitor, CGP-37157, while dibucaine had no apparent effect on Ca2+ recovery. Therefore, inhibition of permeability transition does not appear to be involved in Ca2+ recovery from glutamate-induced Ca2+ loads. 4. Trifluoperazine and dibucaine did not inhibit [3H]-dizocilpine binding at the concentrations that prevented mitochondrial depolarization. 5. These studies suggest that trifluoperazine and dibucaine inhibit permeability transition in intact neurones. Trifluoperazine also appears to inhibit mitochondrial Na+/Ca2+ exchange. These drugs should prove to be valuable tools in the further study of the role of mitochondrial permeability transition in glutamate-induced neuronal death.
Topics: Animals; Benzimidazoles; Calcium; Carbocyanines; Cells, Cultured; Clonazepam; Dibucaine; Dizocilpine Maleate; Fluorescent Dyes; Fluorometry; Glutamic Acid; Membrane Potentials; Mitochondria; Neurons; Prosencephalon; Rats; Rats, Sprague-Dawley; Sodium-Calcium Exchanger; Thiazepines; Trifluoperazine
PubMed: 9384493
DOI: 10.1038/sj.bjp.0701442 -
Biochimica Et Biophysica Acta Dec 1997Mitochondrial permeability transition (MPT) induced by the thiol cross-linker phenylarsine oxide (PhAsO) in Ca(2+)-depleted mitochondria incubated in the presence of...
Mitochondrial permeability transition (MPT) induced by the thiol cross-linker phenylarsine oxide (PhAsO) in Ca(2+)-depleted mitochondria incubated in the presence of ruthenium red, an inhibitor of the Ca2+ uniporter, is stimulated by the addition of extramitochondrial Ca2+. The presence of extramitochondrial Ca2+ stimulates the reaction of mitochondrial membrane protein thiol groups with PhAsO. Both Ca(2+)-induced increase in mitochondrial membrane permeabilization and protein thiol group reaction with PhAsO are dependent on time (5-10 min to be complete) and the concentration of Ca2+ (1-25 microM). Mitochondrial permeabilization induced by PhAsO (15 microM) and extramitochondrial Ca2+ is inhibited by ADP, cyclosporin A, dibucaine and Mg2+, while mitochondrial permeabilization induced by high concentrations of PhAsO (60 microM) in the absence of Ca2+ is inhibited only by ADP and cyclosporin A. These results suggest that dibucaine and Mg2+ can inhibit mitochondrial permeabilization by antagonizing the effect of Ca2+ on the mitochondrial membrane. Once mitochondrial permeabilization induced by 15 microM PhAsO and extramitochondrial Ca2+ has already occurred, the addition of the Ca2+ chelator EGTA restores mitochondrial membrane potential (MPT pore closure), suggesting that the presence of Ca2+ is essential for the maintenance of the permeability of the mitochondrial membrane to protons (MPT pore opening). In conclusion, the results presented indicate that low Ca2+ concentrations acting at the external side of the inner mitochondrial membrane can stimulate mitochondrial permeability transition induced by PhAsO, due to increased accessibility of protein thiol groups to the reaction with PhAsO and increased probability of MPT pore opening.
Topics: Animals; Arsenicals; Calcium; Calcium Channels; Calcium-Binding Proteins; Chelating Agents; Cross-Linking Reagents; Egtazic Acid; Intracellular Membranes; Membrane Potentials; Membrane Proteins; Mitochondria, Liver; Osmolar Concentration; Permeability; Rats; Rats, Wistar; Ruthenium Red; Sulfhydryl Compounds
PubMed: 9452768
DOI: 10.1016/s0005-2728(97)00078-9 -
Biophysical Journal Jun 1997X-ray scattering and electrophysiological experiments were performed on toad sciatic nerves in the presence of local anesthetics. In vitro experiments were performed on...
X-ray scattering and electrophysiological experiments were performed on toad sciatic nerves in the presence of local anesthetics. In vitro experiments were performed on dissected nerves superfused with Ringer's solutions containing procaine, lidocaine, tetracaine, or dibucaine. In vivo experiments were performed on nerves dissected from animals anesthesized by targeted injections of tetracaine-containing solutions. In all cases the anesthetics were found to have the same effects on the x-ray scattering spectra: the intensity ratio of the even-order to the odd-order reflections increases and the lattice parameter increases. These changes are reversible upon removal of the anesthetic. The magnitude of the structural changes varies with the duration of the superfusion and with the nature and concentration of the anesthetic molecule. A striking quantitative correlation was observed between the structural effects and the potency of the anesthetic. Electron density profiles, which hardly showed any structural alteration of the unit membrane, clearly indicated that the anesthetics have the effect of moving the pairs of membranes apart by increasing the thickness of the cytoplasmic space. Electrophysiological measurements performed on the very samples used in the x-ray scattering experiments showed that the amplitude of the compound action potential is affected earlier than the structure of myelin (as revealed by the x-ray scattering experiments), whereas conduction velocity closely follows the structural alterations.
Topics: Action Potentials; Anesthetics, Local; Animals; Biophysical Phenomena; Biophysics; Bufo marinus; Crystallography, X-Ray; Dibucaine; In Vitro Techniques; Lidocaine; Molecular Structure; Myelin Sheath; Neural Conduction; Procaine; Scattering, Radiation; Sciatic Nerve; Tetracaine; X-Rays
PubMed: 9168033
DOI: 10.1016/S0006-3495(97)78901-X -
The Journal of Cell Biology Mar 1997Cells that express wild-type influenza hemagglutinin (HA) fully fuse to RBCs, while cells that express the HA-ectodomain anchored to membranes by...
Cells that express wild-type influenza hemagglutinin (HA) fully fuse to RBCs, while cells that express the HA-ectodomain anchored to membranes by glycosylphosphatidylinositol, rather than by a transmembrane domain, only hemifuse to RBCs. Amphipaths were inserted into inner and outer membrane leaflets to determine the contribution of each leaflet in the transition from hemifusion to fusion. When inserted into outer leaflets, amphipaths did not promote the transition, independent of whether the agent induces monolayers to bend outward (conferring positive spontaneous monolayer curvature) or inward (negative curvature). In contrast, when incorporated into inner leaflets, positive curvature agents led to full fusion. This suggests that fusion is completed when a lipidic fusion pore with net positive curvature is formed by the inner leaflets that compose a hemifusion diaphragm. Suboptimal fusion conditions were established for RBCs bound to cells expressing wild-type HA so that lipid but not aqueous dye spread was observed. While this is the same pattern of dye spread as in stable hemifusion, for this "stunted" fusion, lower concentrations of amphipaths in inner leaflets were required to promote transfer of aqueous dyes. Also, these amphipaths induced larger pores for stunted fusion than they generated within a stable hemifusion diaphragm. Therefore, spontaneous curvature of inner leaflets can affect formation and enlargement of fusion pores induced by HA. We propose that after the HA-ectodomain induces hemifusion, the transmembrane domain causes pore formation by conferring positive spontaneous curvature to leaflets of the hemifusion diaphragm.
Topics: Animals; CHO Cells; Chlorpromazine; Cricetinae; Dibucaine; Erythrocyte Membrane; Fluorescent Dyes; Glycosylphosphatidylinositols; Hemagglutinin Glycoproteins, Influenza Virus; Humans; Lipid Bilayers; Lysophosphatidylcholines; Membrane Fusion; Orthomyxoviridae; Rhodamines
PubMed: 9060465
DOI: 10.1083/jcb.136.5.995 -
The American Journal of Pathology Feb 1997Fluoride (F) is a widely distributed nephrotoxin with exposure potentially resulting from environmental pollution and from fluorinated anesthetic use (eg, isoflurane)....
Fluoride (F) is a widely distributed nephrotoxin with exposure potentially resulting from environmental pollution and from fluorinated anesthetic use (eg, isoflurane). This study sought to characterize some of the subcellular determinants of fluoride cytotoxicity and to determine whether subtoxic F exposure affects tubular cell vulnerability to superimposed ATP depletion and nephrotoxic attack. Human proximal tubular cells (HK-2) were cultured with differing amounts of NaF (0 to 20 mmol/L, overlapping with clinically relevant intrarenal/urinary levels after fluorinated anesthetic use). After completing 24-hour exposures, cell injury was determined (vital dye uptake). Fluoride effects on cell deacylation ([3]H-C20:4 release) and PLA2 activity were also assessed. To determine whether subtoxic F exposure alters tubular cell susceptibility to superimposed injury, cells were exposed to subtoxic NaF doses for 0 to 24 hours and then challenged with simulated ischemia (ATP depletion plus Ca2+ overload) or a clinically relevant nephrotoxic insult (myoglobin exposure). NaF induced dose-dependent cytotoxicity (up to approximately 90% vital dye uptake and increased [3H]C20:4 release). Extracellular Ca2+ chelation (EGTA) and PLA2 inhibitor therapy (aristolochic acid, dibucaine, or mepacrine) each conferred significant protective effects. When subtoxic NaF doses were applied, partial cytosolic PLA2 depletion rapidly developed (approximately 85% within 3 hours, determined on cell extracts). These partially PLA2-depleted cells were markedly resistant to ATP depletion/Ca2+ ionophore injury and to myoglobin-induced attack (approximately 50% decrease in cell death). We conclude that 1) F induces dose-dependent cytotoxicity in cultured human proximal tubular cells, 2) this occurs, in part, via Ca(2+)- and PLA2-dependent mechanism(s), 3) partial cytosolic PLA2 depletion subsequently results, and 4) subtoxic fluoride exposure can acutely increase cell resistance to further attack. Reductions in cytosolic PLA2 activity could potentially contribute to this result.
Topics: Adenosine Triphosphate; Calcium; Cell Survival; Cells, Cultured; Enzyme Inhibitors; Extracellular Space; Humans; Kidney Tubules, Proximal; Myoglobin; Phospholipases A; Phospholipases A2; Sodium Fluoride
PubMed: 9033286
DOI: No ID Found -
Anesthesia and Analgesia Feb 1997Lidocaine and tetracaine suppress superoxide anion (O2-) generation of neutrophils. We examined the effects of eight local anesthetics on O2- generation in human...
Lidocaine and tetracaine suppress superoxide anion (O2-) generation of neutrophils. We examined the effects of eight local anesthetics on O2- generation in human neutrophils and searched for a potential relationship between the biological activities and the physicochemical properties of presently available eight local anesthetics. Human neutrophils incubated with local anesthetic and a Cypridina luciferin analog as a O2(-)-specific chemiluminescence probe were stimulated by phorbol ester. The chemiluminescence development based on O2- generation was monitored by a luminometer. All of the tested local anesthetics suppressed O2- generation in a concentration-dependent manner. The concentration of each of eight local anesthetics that produced 50% inhibition of peak chemiluminescence (IC50) had a rank order of dibucaine < tetracaine < bupivacaine < ropivacaine < procaine < mepivacaine < lidocaine = prilocaine. A linear relationship was obtained between IC50 values and the values of logarithm of partition coefficient (log P) of eight local anesthetics; log (IC50 in molarity) = -1.252 - 0.514 x log P, r2 = 0.891, P < 0.001. Unlike with staurosporine, which inhibits protein kinase C (PKC), no effect was observed on the O2- generation in the presence of tetrodotoxin (TTX), veratridine (VTD), or amiloride. These results suggest that the inhibitory effects of local anesthetics on O2- generation of neutrophils are predicted by physicochemical properties of the drugs, especially partition coefficients.
Topics: Amiloride; Anesthetics, Local; Dose-Response Relationship, Drug; Humans; In Vitro Techniques; Luminescent Measurements; Neutrophils; Superoxides; Tetradecanoylphorbol Acetate; Tetrodotoxin; Veratridine
PubMed: 9024038
DOI: 10.1097/00000539-199702000-00031