Modelling the simultaneous chiral separation of a group of drugs by electrokinetic chromatography using mixtures of cyclodextrins.

Two mixtures of neutral cyclodextrins (CDs) were used in Electrokinetic Chromatography (EKC) to model and optimize the simultaneous enantiomeric separation of a group of seven drugs. Heptakis(2,6-di-O-methyl)-ß-CD (DM-ß-CD) combined with methyl-γ-CD (M-γ-CD) or with carboxyethyl-γ-CD (CE-γ-CD) was employed in a 25 mM formate buffer at pH 3.0 to have the drugs studied positively charged. Dubsky's model was applied to calculate the enantiomer effective electrophoretic mobilities for each combination of CDs at different averaged molar fractions and total CDs concentrations. The most adequate averaged molar fraction and total CDs concentration in terms of the simultaneous enantiomeric separation of the drug mixture were predicted by the model and results were experimentally corroborated. The model also foresaw interesting effects, derived from the combination of DM-ß-CD with M-γ-CD or with CE-γ-CD, on the individual chiral separation of some of the drugs studied. The observed reversal of the migration order for some compounds when changing the total CDs concentration was also predicted and the model showed its potential even at concentrations out of the experimental range of CD concentrations experimentally employed. The use of an averaged molar fraction of 0.8 for DM-ß-CD at a total CDs concentration of 40 mM in the DM-ß-CD/CE-γ-CD system predicted by the model enabled the simultaneous enantiomeric separation of six of the drugs studied (except verapamil) with resolutions ranging from 0.6 to 4.0.

Recent advances on the use of cyclodextrins in the chiral analysis of drugs by capillary electrophoresis.

The most recent advances on the use of cyclodextrins as chiral selectors in capillary electrophoresis for the enantioseparation of drugs are reviewed in this article. The types of cyclodextrins employed and the resolutions achieved are discussed. The use of dual chiral systems, modified capillaries, non-aqueous media or microfluidic devices is also included and the mechanisms for enantioseparation of drugs and the inversion of the enantiomer migration order are studied. The most relevant applications developed to carry out the quantitation of chiral drugs, to assess the enantiomeric purity of pharmaceutical formulations, to study their metabolism or to achieve criminalistic or forensic investigations are described. Articles published in the last six years (period from 2010 to 2015) are considered.

[Spinal granuloma in a patient receiving a spinal infusion of morphine and clonidine]. / Granuloma intradural en un paciente con infusión espinal de morfina y clonidina.

Patients treated with long-term spinal infusion of high doses of morphine develop a granuloma at the location of the catheter tip. Diagnosis is based on a steady increase in intrathecal morphine dosage after a relatively prolonged period of stability, on the gradual development of neurologic signs and symptoms suggesting radicular or spinal cord compression, and on magnetic resonance images. We describe a man with central neuropathic pain after removal of a tumor. The presence of all 3 of the aforementioned diagnostic criteria led to suspicion of a spinal granuloma.

Granuloma intradural en un paciente con infusión espinalde morfina y clonidina / Spinal granuloma in a patient receiving a spinal infusion of morphine and clonidine

Los pacientes en tratamiento con infusión espinal demorfina a dosis elevadas presentan como efecto adversoa largo plazo la formación de un granuloma en la puntadel catéter intradural. La subida ininterrumpida de lasdosis de morfina intratecales tras un periodo relativamenteprolongada de estabilidad, la aparición progresivade una sintomatología neurológica característica decompresión radicular o medular, y las imágenes de resonanciamagnética llevan al diagnóstico de este fenómeno.Se presenta un caso clínico de un paciente con dolor neuropáticocentral tras exéresis tumoral, que reúne los tresprincipios mencionados que llevan al diagnóstico de sospechade granuloma intradural (AU)

Patients treated with long-term spinal infusion of highdoses of morphine develop a granuloma at the locationof the catheter tip. Diagnosis is based on a steadyincrease in intrathecal morphine dosage after arelatively prolonged period of stability, on the gradualdevelopment of neurologic signs and symptomssuggesting radicular or spinal cord compression, and onmagnetic resonance images. We describe a man withcentral neuropathic pain after removal of a tumor. Thepresence of all 3 of the aforementioned diagnosticcriteria led to suspicion of a spinal granuloma (AU)

Detection of bovine whey proteins by on-column derivatization capillary electrophoresis with laser-induced fluorescence monitoring.

1-Anilinonaphthalene-8-sulfonic acid (1,8-ANS), 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (bis-ANS) and 2-(p-toluidino)naphthalene-6-sulfonic acid (2,6-TNS) were evaluated as additives in different buffers for the detection of bovine whey proteins using laser-induced fluorescence (LIF) monitoring in capillary electrophoresis (CE). These N-arylaminonaphthalene sulfonates furnish a large fluorescence emission when associated to some proteins whereas their emission in aqueous buffers, such as those used in CE separations, is very small. To select the best detection conditions, the fluorescence of these probes was first compared using experiments carried out in a fluorescence spectrophotometer. Using bovine serum albumin (BSA) as a model protein, it was demonstrated that 2-(N-cyclohexylamino)ethanesulfonic acid (CHES) buffer (pH 8 and pH 10.2) and the fluorescent probe 2,6-TNS gave rise to the highest increase in fluorescence for BSA. When the composition of these separation buffers was optimized for the electrophoretic separations, CHES buffer, pH 10.2 was chosen as the most suitable buffer to detect bovine whey proteins. The limit of detection obtained for some whey proteins in CE separations was about 6.10(-8) M for BSA, 3.10(-7) M for beta-lactoglobulin A (beta-LGA), 3.10(-7) M for beta-lactoglobulin B (beta-LGB), and 3.10(-6) M for alpha-lactalbumin (alpha-LA). These detection limits were compared to those achieved using UV detection under the same separation conditions. The results showed that the detection limits of BSA, beta-LGA and beta-LGB were twice as good using LIF than with UV detection. However, the limit of detection for alpha-LA was better when UV was used. The applicability of LIF detection to CE separation of whey proteins in bovine milk samples was also demonstrated.

Retention mechanism and implications for selectivity for a group of dihydropyridines in ionic micellar liquid chromatography.

The retention behaviour of a group of dihydropyridines in micellar liquid chromatography was studied using sodium dodecyl sulphate and hexadecyltrimethylammonium bromide as surfactants in the mobile phase containing 5% of n-butanol and a C18 column. When the surfactant concentration in the mobile phase is increased, a tendency to change from a three partition equilibria mechanism to direct transfer of solutes from micelles to the stationary phase is observed for both surfactants. This progressive change in the retention mechanism is explained through the large micellar phase-water partition coefficients of these compounds and the increase produced in the fraction of solute molecules in the micellar phase due to the increase in the volume of this phase originating from the increase in surfactant concentration. As a result, the selectivity coefficients show a tendency to match the ratio of the stationary phase to micellar phase partition coefficients of these compounds, constituting further proof of the progressive change in the retention mechanism when the surfactant concentration is increased.

Effect of cellular Ca2+ loading on alpha 1-agonist or protein kinase C activators-mediated stimulation of phosphorylase "a" in liver cells.

Long chain unsaturated fatty acids stimulate phosphorylase "a" activity in liver cells. Similar degree of activation was achieved by increasing cellular Ca2+ content or by treatment with agents other than oleate, like 1,2-diolein or phorbol esters, sharing in common their ability to activate protein kinase C. In Ca2+-loaded liver cells only phenylephrine was capable of inducing a further stimulation of phosphorylase "a" activity. It is concluded that: 1) The state of activation of protein kinase C may play a role in the hormonal control of liver glycogen metabolism; 2) alpha 1-agonist-mediated activation of phosphorylase "a" can occur by a mechanism which is not related to a Ca2+-dependent activation of protein kinase C.

Role of calcium in the phenylephrine-induced activation of phosphorylase "A" in isolated liver cells.

The ability of phenylephrine to activate phosphorylase in liver cells with variable degrees of Ca2+ loading was studied. Phenylephrine has been found to be capable of stimulating phosphorylase at saturating Ca2+ concentrations that precluded any further action of this ion. Furthermore the degree of activation was proportional to the cellular calcium content. These results allow to conclude that alpha-adrenergic agonists activate phosphorylase by a mechanism apparently unrelated to their ability to mobilize and subsequently increase the cytosolic concentration of free Ca2+.

Characterization of the alpha-adrenergic stimulation of hepatic respiration.

The alpha-adrenergic agonist phenylephrine induces a biphasic stimulation of respiration in perfused isolated rat liver. The first phase, of rapid onset and short duration, is paralleled by increased glycogenolysis, glycolysis, and NAD redox potential. The second phase lasts for as long as the alpha-agonist is present and is accompanied by increased gluconeogenic flux. Only the second phase of sustained increased respiration is clearly dependent on extracellular Ca2+. In contrast, normal respiratory responses were obtained under Ca2+-loading conditions or in the presence of the Ca2+ ionophore A23187, indicating that the alpha-adrenergic action on respiration is not simply mediated by its ability to increase the cytosolic Ca2+ concentration. No stimulation of gluconeogenesis is observed in the absence of a sustained increase of respiration. However, it is not energy support that leads to the stimulation of glucose production. The adrenergic response is influenced by the nutritional status of the animal and the availability of oxidizable fuels. In livers from starved animals, the alpha-adrenergic respiratory response is abolished when long chain fatty acid oxidation is prevented by the addition of tetradecylglycidate. In the presence of pyruvate the respiratory response is partially restored. It is concluded that increased beta-oxidation is not mandatory for the alpha-adrenergic stimulation of respiration; however, maximal respiratory responses are obtained only when fatty acid oxidation is allowed to proceed. The latter finding appears to be the result of a limited flux through the tricarboxylic acid cycle when long chain fatty acid oxidation is impeded, secondary to a limiting acetyl CoA supply.