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Biomedical subjects

L Benes

Publications and source records attributed to L Benes.

At least 73 records · Page 4Linked to original sources
PubMed1986

pH dependence of the blocking activity of carbisocaine and its derivatives.

The blocking activity and pH dependence of carbanilate local anaesthetics, carbisocaine and its homologues, were tested on isolated rat sciatic nerves at pH 6.0, 7.2 and 8.4. Carbisocaine blocked the compound action potential more strongly than the derivatives with shorter alkoxysubstituents. The blocking potency of shorter derivatives increased with the rise of external medium pH, whereas the activity of carbisocaine increased with decreasing external pH. Quaternary compounds applied in the external medium were able to block the action potential, but in higher concentrations and with a longer half-time than their tertiary analogues. The blocking potency of quaternary derivatives correlated well with the length of the alkoxysubstituent and thus also with their lipophilicity. Extracellular pH did not consistently change the inhibitory effect of quaternized derivatives. These observations support the view that the lipophilicity of local anaesthetics is one of the possible factors determining their anaesthetic activity and the pH dependence of their effect.

Action Potentials↗
PubMed1986

Carbamate-induced rhythmic activity in the guinea-pig ileum.

The action of newly synthesised basic esters of alkoxy-substituted derivatives of phenylcarbamic acid was compared with that of procaine and trimecaine in the guinea-pig small intestine. Some of the carbamate local anaesthetics, in concentrations high enough to markedly suppress cholinergic twitches, elicited regular rhythmic activity of the guinea-pig ileum. This effect of the carbamates was dependent on the position of the alkoxysubstituent and was independent of the basic group (pyrrolidine, piperidine or perhydroazepine) present. Only the ortho-substituted derivatives were active. It was also found that the rhythmic activity evoked was of myogenic origin, produced by rhythmic undulations of the sodium-pump activity, accompanied by a potential-dependent change in Ca2+ permeability. It is suggested that the mechanism by which carbamates reveal this endogenous rhythm in the guinea-pig ileum could be a selective block of noncholinergic, nonadrenergic innervation or the TEA-like activity of carbamates.

Anesthetics, Local↗
PubMed1986

Interaction of local anaesthetics with blood platelet aggregation.

The effect of three newly synthesized local anaesthetics on platelet aggregation, serotonin release and integrity of platelets was investigated. Pentacaine, heptacaine and carbisocaine were found to be about 10 times more active than "classic" local anaesthetics. They inhibited platelet aggregation stimulated by collagen, thrombin and ADP at the concentrations of 0.01, 0.1 and 1 mmol/l respectively. At millimolar concentrations the test local anaesthetics liberated serotonin from platelets and disintegrated platelet membranes. Pentacaine was the most effective, followed by heptacaine and carbisocaine. The authors suppose that the perturbation induced in platelet membranes by local anaesthetics could be responsible for inhibition of platelet aggregation and release of serotonin.

Anesthetics, Local↗
PubMed1985

Determination of pentacaine, trans-2-(1-pyrrolidinyl)cyclohexyl-3-pentyloxycarbanilate hydrochloride, in biological samples by gas chromatography/mass spectrometry.

A quantitative and selective method has been developed for the determination of a novel local anaesthetic compound pentacaine, trans-2-(1-pyrrolidinyl)cyclohexyl-3-pentyloxycarbanilate hydrochloride, in biological samples. After ion pair extraction from 1 M HCl into 1,2-dichloroethane, pentacaine and a structurally related internal standard were derivatized to prevent thermal decomposition in the gas chromatograph. An on-column methylation technique with trimethylanilinium hydroxide was used. Determination was performed by gas chromatography/mass spectrometry (GC/MS) with selected ion monitoring. Interferences by endogenous lipophilic constituents were avoided by including an n-hexane wash before the ion pair extraction. This wash step did not reduce the drug recoveries. The method gave linear results over a concentration range of 5-100 ng ml-1 with a coefficient of variation less than 10% at 5 ng pentacaine ml-1. Specimens of plasma, whole blood, urine as well as in vitro preparations such as hepatic microsomes were successfully analysed.

Anesthetics, Local↗
PubMed1985

The rates of replicative and unscheduled DNA synthesis as functions of temperature in LS/B1, L-As and L-C3 cells.

The relative rates of replicative and unscheduled DNA synthesis were determined over a temperature range of 2 degrees to 42 degrees C in LS/B1, L-As and L-C3 cells. The rates were determined by measuring the amount of 3H-dTh incorporated into DNA during 60 min incubation of cells at a given temperature. Acid-resistant 3H-activity incorporated into DNA at 2 degrees C was evaluated as evidence of DNA turnover, not non-specific adsorption of 3H-dTh. The relative rates of RDS and UDS were expressed as functions of temperature and from the data the values of Q10 and Eact necessary for incorporation of one mole of dTh into DNA during RDS and UDS were calculated. The values of Q10 and Eact are comparable to those reported for HeLa, V-79, L5/78Y and the epithelial cells. The experimentally determined values of Q10 and Eact for UDS in the lines tested did not vary. UDS, compared to RDS, is evaluated as a process with lesser demands for energy.

Animals↗
PubMed1985

Changes in DNA capacity for actinomycin-D binding in nuclei of interphase cells.

3H-AMD binding to DNA in interphase nuclei was tested on asynchronous and synchronous LS/BL cell populations under physiological conditions and after exposure to gamma rays (60Co). 3H-AMD binding to DNA in an asynchronous cell population appeared to be nearly constant and independent of 3H-AMD concentration. However, in comparing individual cells, a great variability could be observed. In synchronized cells the DNA accessibility for 3H-AMD binding changed in the course of the cell cycle, with a maximum occurring at the late G1-phase (13.95 X 10(-12) mumol/nucleus) and a minimum at the late G2-phase (2.63 X 10(-12) mumol/nucleus). In irradiated cells the DNA capacity for 3H-AMD binding was growing with the increasing dose (5-80 Gy) from 4.9 to 11.2 X 10(-12) mumol 3H-AMD/nucleus.

Animals↗
PubMed1985

Absorption of pentacaine from ulcerous rat stomach.

Pentacaine is a local anaesthetic which exhibited positive effects on healing of model ulcers in the rat stomach. The in situ disappearance of pentacaine from the ulcerous and intact rat stomach was studied. Gastric ulcers were produced by oral administration of phenylbutazone (200 mg . kg-1) 3.5 h before absorption experiment. Pentacaine exhibited a biexponential decrease from the lumen of the stomach, the rate of which was essentially the same in both groups. The total amount of pentacaine absorbed was small because of extremely low absorption rate.

Absorption↗
PubMed1984

Perturbation effect of local anaesthetics on synaptosomes: variation with depth of the spin label probe.

Stearic acids labeled with a doxyl group at the 5th, 12th and 16th carbon positions were used as the spin probes for an investigation of the perturbation effects of two local anaesthetics (the 2-piperidinoethylester of phenyl carbamic acid and the piperidinoethylester of 2-heptyloxyphenylcarbamic acid) on rat brain synaptosomes. For a quantitation of the perturbation effects we have studied the order parameter S of the spin probe, incorporated in the membrane, calculated from the ESR spectra as a function of temperature and concentration of local anaesthetics. The local anaesthetics had a different disordering efficiency at different depths of the membrane. It follows from our results that the perturbing effects of the anaesthetics increase relative to the depth of the membrane, and the extent of perturbation correlates with local anaesthetic activity.

Anesthetics, Local↗