A comparison of the local anaesthetic effects of cationic, anionic, and neutral amphipathic agents in frog skeletal muscle

Impermeant alkyl amphipathic agents reduced the excitability of frog twitch muscle fibers, indicating that local anaesthesia can be produced by perturbations within the external lamina of the sarcolemma. Cationic (n-alkyl trimethylammonium) and anionic (n-alkyl sulfonate) as well as permeant neutral (n-alkanol) agents have been compared with regard to their local anaesthetic potency. Small impermeant agents (fewer than six carbon atoms) alone were ineffective. Within each series the concentration required to reduce excitability was proportional to the length (hydrophobicity) of the hydrocarbon chain attached to the polar group. However, corresponding members of these three series of compounds differed considerably in their local anaethetic potency. Hence, charged groups as well as apolar moieties can influence local anaesthetic efficacy. The supra-additive character of the local anaesthesia produced by combining impermeant alkyl anions and cations indicates that these two types of amphipaths may produce their similar effects by perturbations at different membrane sites.     

Transport of local anaesthetics across chromatophore membranes.

1. Both simple amines and tertiary amino local anaesthetics give rise to an accelerated decay of the absorption change of added pH indicator dyes and a decelerated decay of the endogenous carotenoid absorption band shift, following short flash excitation of Rhodopseudomonas sphaeroides chromatophores. 2. With increasing medium pH, lower concentrations of amine or local anaesthetics are effective. 3. The order of potency of the local anaesthetics concurs with their reported membrane/buffer partition coefficients and concentrations required for action potential blockade in nerve fibres. 4. The data are taken as evidence for rapid transport of the free base across the chromatophore membrane and relatively slow penetration of the protonated local anaesthetic. Protolytic reactions complete the effective dissipation of the trans-membrane pH gradient. 5. Benzocaine, with its unusually low pKa and the quaternary derivative, chloropromazine methiodide do not display this type of behaviour. 6. In the presence of membrane potential-collapsing agents, such as valinomycin/K+ or thiocyanate ions, local anaesthetics decelerate the decay of the cresol red change but have no effect on the carotenoid shift decay. It appears that transport of the unprotonated local anaesthetic although electrically neutral, requires the presence of a membrane potential. 7. In contrast, the non-anaesthetic amines act independently of the membrane potential. 8. Ca2+ interferes with the mechanism of local anaesthetic deceleration of the cresol red change decay in the presence of valinomycin/K+ or thiocyanate but not with other anaesthetic or amine reactions.     

Action of local anaesthetics on passive and energy-linked ion translocation in the inner mitochondrial membrane

The effect of dibucaine on passive and respiration-driven ion translocation and oxidative phosphorylation in submitochondrial particles from beef-heart has been studied.Dibucaine inhibited the nigericin-mediated H⁺/K⁺ exchange diffusion and the electrogenic, valinomycin-mediated K⁺ translocation in submitochondrial particles.The local anaesthetic exerted a direct stimulatory effect on the respiration-driven proton uptake and on the passive proton-diffusion reactions. The increase of the respiration-linked proton turnover caused by dibucaine was accompanied by uncoupling of oxidative phosphorylation. It is concluded that spontaneous noncoupled as well as ionophoremediated K⁺ translocation in mitochondria occurs across phospholipid bilayer regions of the membrane whilst other components of the membrane would be specifically involved in active and passive proton translocation across the membrane.The results indicate that polar groups of membrane phospholipids play an important role in energy conservation and transfer in the mitochondrial membrane.     

The effect of local anaesthetic agents on lipolysis by human adipose tissue

Prilocaine chloride, a common local anaesthetic agent with free tertiary amino groups, was shown to 1) inhibit the basal as well as the stimulated lipolysis by human subcutaneous and omental adipose tissue and 2) abolish the antilipolytic effect of insulin on these processes. A way of avoiding these undesirable effects of the local anaesthetic agent when injected $\text{in vivo}$ is described.     

Noninvasive cardiac output and blood pressure monitoring cannot replace an invasive monitoring system in critically ill patients

Background

Sub-Tenon's anaesthetic is effective and reliable in producing both akinesia and anaesthesia for cataract surgery. Our clinical experience indicates that it is sometimes necessary when absolute akinesia is required during surgery to augment the block with 1–2 ml of local anaesthetic. Hypothesis was that after first injection some of the volume injected may spill out and before second injection the effect of hyaluronidase has taken place and second volume injectate will have desired effect.

Methods

A prospective, randomised, control trial in which patients were randomly allocated to one of two groups. In group 1, single injection of 5 ml of local anaesthetic was injected. In group 2, 3 ml of the same anaesthetic solution was injected followed by application of gentle orbital pressure for 2 minutes. A further 2 ml of the same anaesthetic solution was injected through the same conjunctival incision. Measurement of movement in four quadrants of eye was done by the surgeon at 3 and 6 minutes. Intraocular pressure, chemosis, and subconjuctival haemorrhage were also measured.

Results

Significant differences at 3 minutes between groups for overall movement, medial, superior, and lateral quadrants occurred. At 6 minutes no significant group differences emerged for the overall movement or for any of four quadrants.

Conclusion

Single injection of local anaesthesia for sub-Tenon's block with mixture of lignocaine with adrenaline, bupivacaine and hyaluronidase was found to be superior to provide akinesia of ocular muscles compared to divided dose given by two injections. No difference in groups in terms of haemorrhage, chemosis, patient's satisfaction and intraocular pressure was found.

Trial registration

Trial registration no-ISRCTN73431052     

Change in membrane fluidity induced by polyphenols is highly dependent on the position and number of galloyl groups

The cell membrane fluidity was very important in adipogenesis and galloyl groups on polyphenolic structures could enhance their antiadipogenic activity. However, the effect of polyphenols on membrane fluidity and the role of galloyl groups in fluidity changes remain unclear. Therefore, the present study chose structurally different polyphenols to compare their effects on the membrane morphology and fluidity of 3T3-L1 preadipocytes, and then the reasons behind the changes of membrane fluidity induced by galloylated polyphenols were explored from structural and molecular insights using liposome model and molecular dynamic simulation technology. Our results indicated that galloylated polyphenols could significantly change 3T3-L1 cell membrane morphology and decrease membrane fluidity, while non-galloylated ones could not. The membrane interference effect of polyphenols was enhanced as the number of galloyl groups increased. Morever, the decrease in membrane fluidity induced by galloylated polyphenols was due to the disturbance of polyphenols on lipid alkyl chains in the cell membrane. Galloylated polyphenols could not only locate in the polar head, but also insert into hydrophobic center of lipid bilayer to interfere with the lipid alkyl chains arrangement, thus decreasing the membrane fluidity and showing strong affinity for the membrane. In addition, differences in position of galloyl groups in polyphenols induced distinct effect on cell membranes interactions, thus affecting the binding manner and bioactivity. The results expanded the understanding on the strong antiadipogenic activity of galloylated polyphenols through the aspect of their effects on cell membrane by both experimental and theoretically simulated ways.     

Direct determination by 2H-NMR of the ionization state of phospholipids and of a local anaesthetic at the membrane surface

Protonation and deprotonation of the primary amino group of phosphatidylethanolamine, and of the lipid phosphate groups of phosphatidylethanolamine with phosphatidylcholine, have been observed directly and isothermally in equimolar mixed fluid bilayers of the two phospholipids. In addition, the acid-base titration of the secondary amino group of the local anaesthetic, tetracaine, whilst partitioned into the bilayers, has also been determined. Here we show how studies by deuterium nuclear magnetic resonance of non-perturbing deuterons, specifically placed at the membrane polar-apolar interface, can give direct information about the electrostatics at a membrane surface.     

The effect of butacaine on adenine nucleotide binding and translocation in rat liver mitochondria.

The effect of the local anaesthetic, butacaine, on adenine nucleotide binding and translocation in rat liver mitochondria partially depleted of their adenine nucleotide content was investigated. The range of butacaine concentrations that inhibit adenine nucleotide translocation and the extent of the inhibition are similar to the values obtained for native mitochondria. Butacaine does not alter either the total number of atractyloside-sensitive binding sites of depleted mitochondria, or the affinity of these sites for ADP or ATP under conditions where a partial inhibition of the rate of adenine nucleotide translocation is observed. The data are consistent with an effect of butacaine on the process by which adenine nucleotides are transported across the mitochondrial inner membrane rather than on the binding of adenine nucleotides to sites on the adenine nucleotide carrier. The results are briefly discussed in relation to the use of local anaesthetics in investigations of the mechanism of adenine nucleotide translocation.     

Effect of 8-alkylberberine homologues on erythrocyte membrane

8-alkylberberine homologues (Ber-C8-n, where n indicates carbon atom number of gaseous normal alkyl at 8 position, n = 0, 2, 4, 6, 8, 10, 12, or 16) were synthesized and their effects on the hemolysis of rabbit erythrocyte, the fluidity of membrane and the fluorescence of membrane protein were investigated by fluorescence analysis technique. Ber-C8-n with mediate length alkyl (4 < n < 10) exhibited obvious hemolysis effect on rabbit erythrocyte when their concentration exceed 1.25 x10(-4) mol/L, and Ber-C8-8 displayed the highest hemolysis effect among all tested homologues. All of Ber-C8-n influenced the fluidity of erythrocyte membrane to different extents, which exhibited an obvious dose-effect relationship. The effect of Ber-C8-n on fluidity increased as the length of alkyl chain was elongated and decreased gradually when the alkyl carbon atoms exceeded 8. The fluorescence of erythrocyte membrane protein was quenched by Ber-C8-n, which showed a similar changing tendency on membrane fluidity. Experiments in vitro suggested that disturbing effects of Ber-C8-n on the conformation and function of membrane protein leaded to the changes of membrane fluidity and stability, and then the membrane was broken down.     

Orcadian Changes in Stimulus Threshold and in the Effect of a Local Anaesthetic Drug in Human Teeth: Studies with an Electronic Pulptester

An electronic puiptester with constant testing current was used to study the stimulus threshold in human teeth of 28 healthy volunteers and the duration of local anaesthesia by articaine plus epinephrine in 55 patients with caries who underwent a filling therapy. In 21 out of the 28 volunteers, significant daily variations in stimulus threshold were detected by cosinor analysis. Acrophases, however, were scattered over the 24-hr scale. In patients, the local anaesthetic effect was studied at four different times of day (0800,1100,1400 and 1700 hr). The electronic device allowed one to accurately determine the time to peak effect (T_max), duration of effect (E_max, time to return to baseline threshold (T_ret) and the area under the time-effect curve (AUC) as a measure of the total local anaesthetic effect. Significant diurnal variations in AUC and E_max were found in 36 patients with the 0.8 ml dose, with peak and trough values at 1400 and 1700 hr, respectively. No differences in effect were found with the low dose of 0.4 ml applied to 19 patients either at 1400 or 1700 hr giving evidence for a circadian phase-dependency in the dose-response relationship of a local anaesthetic drug. The results clearly demonstrate that this electronic device is suitable for exact evaluation of circadian changes in local anaesthetic effects. Under drug-free control conditions, however, the low stimulus frequence of 5 Hz of this device obviously does not allow to discriminate between stimuli modified by pain perception and/or alertness.     

Mechanism of action of βadrenergic receptor blocking agents in angina pectoris: Comparison of action of propranolol with dexpropranolol and practolol

The effect on exercise tolerance of racemic propranolol has been assessed in eight angina pectoris patients and compared with that of dexpropranolol (the dextro isomer of propranolol), practolol (I.C.I. 50172), and saline. Dexpropranolol has the same local anaesthetic action as propranolol with negligible β-adrenergic receptor blocking activity, while practolol is a cardio-selective β-adrenergic blocking agent which does not have local anaesthetic activity.Saline and dexpropranolol had no significant effect on exercise time; racemic propranolol and practolol improved exercise tolerance in six subjects, the response to the two drugs being very similar in individual patients. It was concluded that the beneficial effect of propranolol in angina pectoris results from its action as a β-adrenergic receptor blocking agent and is not due to its local anaesthetic, or quinidine-like, activity.     

Influence of anaesthetic drugs on the epididymal sperm quality in domestic cats

The present study investigated the effect of different anaesthetic agents commonly used in cats on the fresh and frozen-thawed epididymal sperm. Seventeen male domestic cats were castrated using pentobarbital, ketamine HCl or isoflurane. Sperm samples were recovered from epididymides and evaluated before and after freezing, determining the vigor, motility, morphology, acrosome status, sperm viability and functional membrane integrity. Fresh epididymal sperm was influenced by the drugs used, noting that motility features, i.e. vigor (p≤0.05) and progressive motility (p≤0.05), were higher for the inhalation anaesthetic while the others did not showed statistical differences. In frozen-thawed sperm samples, cats treated with barbiturics showed lower values for acrosome status (p≤0.05) and integrity and functionality of membrane (p≤0.05 and p≤0.01, respectively) than in the others groups. Results suggested that drugs used for castration in cats could affect the sperm quality and this should be considered when implementing sperm cryopreservation in the feline.     

Acetylcholine receptor. Binding properties and ion permeability response after covalent attachment of the local anaesthetic quinacrine.

Membrane vesicles rich in nicotinic acetylcholine receptor prepared from Torpedo californica electric tissue have been irreversibly modified with quinacrine mustard, an alkylating derivative of the local anaesthetic quinacrine. The reaction blocked the ion channel regulated by the acetylcholine receptor. Acetylcholine still bound to the modified membrane vesicles with KD approx. 10(-8). The number of binding sites was reduced by up to 50%. Stopped-flow experiments showed that in contrast to what had been found with the reversibly binding quinacrine no fluorescence changes caused by energy transfer from the irradiated protein to the fluorescent local anaesthetic occurred after addition of agonist. This indicates that the conformational changes associated with the activation of the ion channel are blocked by the covalent reaction with quinacrine mustard. Analysis of the membrane vesicles by SDS-polyacrylamide gel electrophoresis showed that all polypeptide chains assumed to be part of the receptor complex had reacted with the mustard. Even small components, probably lipids, migrating with the dye front, showed fluorescence.     

Antibacterial and antifungal efficacy of surface functionalized polymeric beads in repeated applications

A simple method was developed to prepare polymeric microbeads with antibacterial and antifungal properties. The microbeads of approximately spherical shape and narrow size distribution were prepared from a mixture of poly (4-vinyl pyridine) (P4VP) and poly (vinylidene fluoride) (PVDF) by a phase inversion technique and subsequently derivatized with alkyl bromides having 4-10 carbon atoms. The quaternization of the pyridine groups into pyridinium groups confers the surface with highly effective and long-lasting antibacterial and antifungal properties, as shown by the effect on Escherichia coli and Aspergillus niger. Upon contact with the N-alkylated beads, the bacteria and fungal spores are lysed and intracellular constituents leach out into the medium. The efficacy of the alkyl chains in disrupting the cell membrane was investigated. The stability of the functional group and microbiocidal effectiveness of the microbeads in repeated applications was also assessed.     

Dibucaine-induced synchronous mucocyst secretion in Tetrahymena

Synchronous secretion of all available mature mucocysts was induced in late log phase cultures of Tetrahymena thermophilia (B III) by the local anaesthetic dibucaine. No assembled fusion rosettes were seen within the plasma membrane after release until 2-3 hrs of regrowth, thus proving that the rosettes are not permanent sites within the plasma membrane but have to be reassembled each time for a new fusion event to occur. Concomitant with the reappearance of assembled fusion rosettes, the cell cytoplasm fills up with precursors of new mucocysts thus linking the two events together.     

Hydrophobicity, topography in membranes and photosensitization of silicon phthalocyanines with axial ligands of varying lengths.

Six amphiphilic silicon phthalocyanines (SiPc's) axially linked to a dimethylated amino alkyl group of varying length have been examined for their potential suitability as photosensitizers for photodynamic therapy (PDT). This group of molecules was chosen because the length of the axial ligand might place the chromophoric part of the molecule at different vertical depths in the membrane and possibly affect the extent of membrane localized damage caused by singlet oxygen. We tested the relative penetration depth of the SiPc groups in the membrane by the extent to which their fluorescence was quenched by external iodide ions. We also measured singlet oxygen quantum yields of the SiPc's in a liposome membrane, using the fluorescent target for singlet oxygen, 9,10-dimethylanthracene. The hydrophobicity parameters, LogP, were calculated and were also measured. Some correlation was found between them and Kb's, the binding constants for liposomes. The effect of the axial ligand's length is less striking than in similar cases with hematoporphyrins and protoporphyrins. We link this smaller effect with a bending of the linker chain that enables, sterically, a better positioning of the sensitizer molecules within the ordered lipid layer structure.     

Side Effects of Long-Acting Local Anaesthetics in Patients with Preexisting Cardiovascular Condition

The oral surgical anaesthesia is field in which usually long-acting local anaesthetics are being used. Some of the currently used acting local anaesthetics as Levobupivacaine or Ropivacaine have reduced cardiac toxicity. The aim of this review is to provide an overview of acting mechanisms when anaesthetic agents are applied in oral surgery and the effect that they may have in patients with chronic concurrent cardiac conditions. There are notable linking the property of the local anaesthetics lipid solubility and the potency of local anaesthetic-induced vasoconstriction which can additionally compromise cardiac function in patients with previously impaired cardiac function.     

Effect of Neostigmine on Integrity of Ileorectal Anastomoses

Patients undergoing total colectomy and ileorectal anastomosis for chronic ulcerative colitis were divided into two groups depending on whether neostigmine was administered during the anaesthetic to reverse the muscle relaxant. Those receiving neostigmine showed a postoperative anastomotic leakage rate of 36%. In the group not receiving neostigmine the leak rate was 4%, an apparently highly significant difference. Neostigmine may produce this effect by causing contractions of the gut musculature or by vasoconstriction of the blood vessels to the suture line, resulting in local ischaemia.     

Local anaesthetics and nodal polyanions in peripheral nerve

Synopsis Pantocaine, procaine, xylocaine and cocaine were found to interact with the polyanionic matrix surrounding the nodal axon membrane of peripheral myelinated nerve. Their affinity for nodal anionic sites was found to lie between that of mono- and divalent inorganic cations. The affinity was related to the polar character of local anaesthetic molecules. The possible significance of these interactions is discussed in terms of current theories regarding the action of local anaesthetics on nerve impulse conduction.