Obstructive sleep apnea in children with epilepsy: prospective pilot trial.

BACKGROUND: Obstructive sleep apnea (OSA) is prevalent in adults with epilepsy, especially refractory, but limited data exist in children with epilepsy. AIMS: We conducted a prospective pilot study in children with epilepsy to identify the prevalence of OSA and its relationship to the use of antiepileptic drugs (AEDs) and epilepsy types. METHODS: We used Michigan Pediatric Sleep Questionnaire (PSQ) in children with epilepsy. Patients were classified by seizures frequency as mild (0-1 seizure/month) or severe, refractory epilepsy (> 1 seizures/month). We used PSQ ≥ 0.33 as a cutoff point to assess the risk of OSA. RESULTS: Of 84 children, 52 were classified as mild and 32 as severe. Prevalence of OSA was significantly higher in the severe (43.8%) vs the mild group (30.7%, P < 0.05). Children on >1 AED had significantly higher prevalence of OSA (45.8%) than children on ≤1 AED (30.6%, P < 0.05). There was no significant correlation between the prevalence of OSA and seizure types. CONCLUSIONS: OSA is more prevalent in refractory epilepsy and in children who are on multiple AEDs. While further studies are needed to confirm these findings and to assess the consequences of OSA, we believe it is important to screen the children with epilepsy for OSA.

Quantitative determination of catecholamines in individual bovine adrenomedullary cells by reversed-phase microcolumn liquid chromatography with electrochemical detection.

A microcolumn liquid chromatographic method for the determination of norepinephrine and epinephrine in single bovine adrenomedullary cells is described. A single cell is isolated from a culture plate, (3,4-dihydroxybenzyl)amine is added as an internal standard, and the cell is lysed with perchloric acid. After centrifugation, the supernatant is injected directly into a 42 or 50 microns Inner diameter C18 reversed-phase column operated with electrochemical detection. Detection limits for norepinephrine and epinephrine were 46 and 75 amol, respectively. Of the 22 cells examined, 8 contained predominantly norepinephrine, 10 contained predominantly epinephrine, and at least 4 cells contained significant amounts of each. On average, a single cell contained approximately 150 fmol of catecholamine.

Temporally resolved catecholamine spikes correspond to single vesicle release from individual chromaffin cells.

Secretion of catecholamines from single bovine chromaffin cells in culture was elicited by brief pressure ejections from a micropipette containing nicotine, carbamoylcholine, or potassium ions or by mechanical stimulation. Release was monitored electrochemically with a carbon-fiber microelectrode placed adjacent to the cell. Cyclic voltammetry was used to identify secreted species, whereas constant potential amperometry was used for improved temporal resolution (millisecond range) of catecholamine detection. During secretion, brief current spikes were observed, which were shown to be due to detection of catecholamines by electrooxidation. The spikes have the physical characteristics of multimolecular packets of catecholamines released at random times and locations from the surface of the single cell. The half-width of the spikes was found to increase with an increase in cell-electrode spacing. The properties of the catecholamine spikes correlate well with expectations based on secretion from individual storage vesicles. Spikes do not occur in the absence of Ca2+ in the buffer, and the majority of spikes are found to be distributed between 0.2 and 2 picocoulombs, corresponding to 1-10 attomoles of catecholamine detected. The frequency of the spikes increases with the intensity of the stimulus, but the average quantity of catecholamine in each spike is independent of the stimulus. Thus, these measurements represent time-resolved observation of quantal secretion of catecholamines and provide direct evidence for the exocytotic hypothesis.

Secretion of catecholamines from individual adrenal medullary chromaffin cells.

Catecholamine secretion has been measured with electrochemical techniques from isolated, single adrenal medullary chromaffin cells with carbon-fiber microelectrodes. The electrode tip, which is of similar dimensions to the cell, is placed adjacent to the cell to enable the measurement of local secretion. Secretion is caused by exposing the cell to nanoliter volumes of solution containing nicotinic receptor agonists or depolarizing agents. The identification of secreted substances is made with cyclic voltammetry at both bare electrodes and electrodes coated with a perfluorinated cation-exchange polymer. Catecholamine secretion is induced by nicotine (10-500 microM), carbamylcholine (1 mM), and K+ (60 mM). All agents that induce secretion lead to a broad envelope of secreted catecholamines on which sharp concentration spikes are superimposed. The concentration spikes can be monitored with a time resolution of tens of milliseconds when the electrodes are used in the amperometric mode. Release induced by nicotine and K+ is inhibited by Cd2+ (0.5 mM), and hexamethonium selectively blocks the nicotine-induced secretion. The actions of nicotine are found to continue for a longer period of time than those of the other secretagogues tested.

Nicotinic receptor-mediated catecholamine secretion from individual chromaffin cells. Chemical evidence for exocytosis.

Nicotinic receptor-mediated secretion of catecholamines from individual cultured bovine adrenal medullary chromaffin cells was measured and characterized with a voltametric microelectrode placed adjacent to the cells. Nicotine-induced secretion is associated with a large increase in chemical spikes that is temporally resolved into the apparent secretion of discrete packets of attomole quantities of easily oxidized molecules. These data are consistent with direct chemical measurement of single exocytotic events.