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ABSTRACT: Microcolumn liquid chromatography (LC) was interfaced with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) for separation and identification of peptides present in single neurons from the brain of the snail Lymnaea stagnalis. The nanoliter microcolumn LC effluent, mixed off-line with nanoliter matrix solution, was deposited onto the sample target every 60 s, producing fractions of approximately 145 nL in volume, which, upon drying, produced spots of approximately 1 mm in size. At the end of the chromatographic separation, fractions from the sample target were scanned by MALDI-TOF-MS. Identification of peptide peaks was achieved on the basis of LC elution order and mass information. Further identification based on sequence information was carried out for a native peptide fractionated by microcolumn LC from a single neuron with the postsource decay technique.
Analytical Chemistry 06/1998; 70(9):1847-52. · 5.86 Impact Factor
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ABSTRACT: Corelease of histamine and 5-hydroxytryptamine from individual mast cells has been measured with fast-scan cyclic voltammetry using a carbon-fiber electrode placed next to a single cell. Release events, induced by exposure of the cells to the calcium ionophore, A23187, were resolved at the level of individual exocytotic events. Changes in the relative concentrations secreted from individual granules were observed after incubation with 5-hydroxytryptamine, histamine, and tryptophan. In contrast, an alteration in individual cell content after such incubations, analyzed with capillary chromatography, was only found after incubation with 5-hydroxytryptamine. Cells incubated with 5-hydroxytryptamine or its precursor, tryptophan, released more 5-hydroxytryptamine and less histamine per secretory event relative to controls. Coincubation of the cells with pargyline and 5-hydroxytryptamine further reduced the release of histamine. Since cell content of histamine is unchanged, the reduction in its release must be due to its displacement to a nonreleasable compartment induced by 5-hydroxytryptamine granular uptake. Incubation with histamine increased histamine secretion and, surprisingly, also increased 5-hydroxytryptamine release without changing its cell content. This result is consistent with a relaxation of the storage matrix accompanying histamine granular uptake allowing more 5-hydroxytryptamine to be released. These results demonstrate that the intragranular mode of storage as well as granular uptake of biogenic amines affects the stoichiometry of their release.
Biochemistry 02/1998; 37(4):1046-52. · 3.42 Impact Factor
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ABSTRACT: A microcolumn liquid chromatography method for determining norepinephrine (NE), epinephrine (E), and phenylethanolamine N-methyltransferase (PNMT) enzyme activity in single bovine adrenal medullary cells is presented. Single cells were isolated and treated with excess deuterated substrate, D3-NE (0.05 mM) for enzyme reaction. After 6 h, the reaction was quenched and the product, D3-E, was quantified along with endogenous NE and E. Separation and detection of deuterated and protiated NE and E were achieved with microcolumns (110-125 cm long, 25 microns inner diameter) packed with 3 microns octadecylsilane-modified particles and operated with amperometric detection. Of the 33 cells reported, most cells containing predominantly E have enzyme activity while cells containing predominantly NE and cells containing a mixture of both NE and E show no enzyme activity. After incubation with 10 microM hydrocortisone, of the 17 cells reported, most cells containing predominantly E and cells containing a mixture of both NE and E have enzyme activity while cells containing predominantly NE have no enzyme activity. Detection limits for NE and E were 42 and 48 amol, respectively.
Analytical Chemistry 11/1997; 69(19):3907-14. · 5.86 Impact Factor
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ABSTRACT: Fused silica capillary liquid chromatography columns with inner diameters between 12 and 33 microns were slurry packed with 5 microns octadecylsilane-modified silica particles. Column efficiencies and van Deemter coefficients were compared. A linear decrease of the A term as column diameter was decreased was the most significant contributor to a lower overall plate height at the optimum velocity.
Analytical Chemistry 05/1996; 68(7):1212-7. · 5.86 Impact Factor
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ABSTRACT: The electrochemical oxidation of histamine has been investigated as an analytical tool. In a physiological buffer, histamine is oxidized at carbon fiber microelectrodes at potentials close to the background in a chemically irreversible process. Cylindrical carbon fiber electrodes were used as amperometric detectors for histamine separated with a reversed-phase capillary column, and detection limits of 240 amol were achieved. Electrodes with beveled tips were used as real-time sensors by monitoring with repetitive cyclic voltammograms at a scan rate of 800 V/s with a 16.7-ms repetition rate, and detection limits of 1.4 microM were achieved. Both techniques were used to probe histamine and 5-hydroxytryptamine (5-HT) stored in rat peritoneal mast cells. The content in single cells was measured by capillary HPLC, and both substances were found in single cells. Although the analysis revealed a large cell-to-cell variation in the amount of histamine and 5-HT, the average amount was 150 and 4 fmol of histamine and 5-HT, respectively. Release of histamine and 5-HT was measured with the electrode placed 1 microm from the cell surface. Release was observed as a series of sharp concentration spikes, consistent with corelease of the two substances from individual vesicles following exocytosis.
Analytical Chemistry 01/1996; 67(24):4514-21. · 5.86 Impact Factor
