Automated DNA purification for fluorescent sequencing.
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Automation↗
Biomedical subjects
C Lear
Publications and source records attributed to C Lear.
Differential electron capture mass spectral response of pentafluorobenzoyl derivatives of platelet activating factor alkyl chain homologs.
The electron capture mass spectrometric response of pentafluorobenzoyl ester derivatives of platelet-activating factor alkyl chain homologs has been found to be inversely proportional to their alkyl chain length. This phenomenon was observed when either the gas chromatograph or direct insertion probe was utilized for sample introduction. A similar differential response was also obtained for a series of fatty alcohols, analyzed as pentafluorobenzoyl esters. These studies demonstrate that multiple standard curves must be prepared for analysis of platelet-activating factor and related lipids in order to obtain accurate quantification.
Benzoates↗
Radiation-induced increased platelet-activating factor activity in mixed saliva.
BACKGROUND: Platelet-activating factor (PAF), a family of structurally-related phospholipid mediators of inflammation, is present in normal human mixed saliva; however, its role in oral biology and the homeostasis of oral host defense mechanisms remains to be established. EXPERIMENTAL DESIGN: The current study was designed to evaluate the salivary levels of PAF in patients with oral mucositis that developed as a complication of head and neck irradiation for oral cancer. PAF activity was assessed in platelet bioassay and expressed relative to the activity of authentic PAF, 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (C16:0-AGEPC). RESULTS: A significant increase in salivary PAF levels was observed in patients with mucositis (47,032 +/- 12,731 C16:0-AGEPC fmole equivalents/ml of saliva, mean +/- SE, N = 7) as compared with normal subjects (5,568 +/- 1,135 C16:0-AGEPC fmole equivalents/ml of saliva, N = 27). Phospholipid fractionation of the PAF isolated from the saliva of patients with mucositis by reverse phase high performance liquid chromatography revealed a single peak of activity that corresponded with the elution profile of C16:0-AGEPC, the most biologically active molecular species of PAF. In contrast, the PAF isolated from normal human mixed saliva contained multiple molecular species of PAF. CONCLUSIONS: These results suggest that this potent phospholipid inflammatory mediator may play a role in the inflammation and tissue injury associated with mucositis resulting from radiation treatment for oral cancer.
Humans↗
Differential responsiveness of human neutrophils to the autocrine actions of 1-O-alkyl-homologs and 1-acyl analogs of platelet-activating factor.
The phlogistic actions of six molecular species of platelet-activating factor (PAF) (1-O-alkyl-PAF homologs, 16:0-, 18:0- and 18:1-alkyl-PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC) and their respective 1-acyl-PAF analog counterparts, 16:0-, 18:0- and 18:1-acyl-PAF, 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (AGPC)) were assessed relative to five human neutrophilic polymorphonuclear leukocyte (PMN) functional responses: 1) lysosomal enzyme secretion; 2) specific desensitization to 16:0-AGEPC-induced lysosomal enzyme secretion; 3) O2- production; 4) chemotaxis; and 5) priming for enhanced O2- production. With respect to inducing lysozyme secretion, 18:0-AGEPC was 30- and 75-fold less potent than 16:0-AGEPC and 18:1-AGEPC, respectively, and was 25- and 40-fold less potent for inducing beta-glucuronidase secretion. 18:0-AGEPC was also 10-fold less active than 18:1- and 16:0-AGEPC for inducing O2- production. Thus, the rank order of potency of the alkyl-PAF homologs for inducing both lysosomal enzyme secretion and O2- production was 18:1- greater than or equal to 16:0- much greater than 18:0-AGEPC. In contrast, these three alkyl-PAF homologs had the same potency for desensitizing PMN to subsequent 16:0-AGEPC-induced lysosomal enzyme secretion and for priming PMN for augmented O2- production in response to FMLP or human recombinant C5a. Paradoxically, however, the rank order of potency of the alkyl-PAF homologs for effecting PMN chemotaxis was 18:0- greater than 18:1- much greater than 16:0-AGEPC. At concentrations as high as 1.0 microM, the acyl-PAF analogs did not initiate PMN lysosomal enzyme secretion, O2- production, or chemotaxis. However, the acyl-PAF analogs induced partial PMN desensitization to 16:0-AGEPC. A novel finding of potential (patho)-physiologic significance was the ability of acyl-PAF at nM concentrations to prime PMN for significantly enhanced O2- production after stimulation with FMLP or human recombinant C5a. The priming action of acyl-PAF was due to an increase in the rate as opposed to a prolongation of O2- production. The differing rank orders of potency of the alkyl-PAF homologs and acyl-PAF analogs for stimulating several physiologic responses of the same target cell, the human PMN, support the premise that there may be more than one PAF receptor subtype on the PMN and/or that differences in the biophysical properties of the various molecular species of PAF modulate their interaction with PAF receptor(s) linked to stimulus-response coupling.
Acylation↗
Fast atom bombardment-mass spectrometric identification of molecular species of platelet-activating factor produced by stimulated human polymorphonuclear leukocytes.
Fast atom bombardment mass spectrometry was used to identify molecular species of platelet-activating factor (PAF) produced by stimulated human neutrophilic polymorphonuclear leukocytes. Normal and reverse-phase high performance liquid chromatography were employed to separate the individual regions with PAF activity prior to mass spectrometric analysis. The following alkyl chain homologs of acetyl glyceryl ether phosphorylcholine (AGEPC) were found: C16:0, C17:0, C18:0 and C18:1. There was also evidence for the presence of the C15:0 homolog, as well as other species which have not yet been identified.
Chromatography, High Pressure Liquid↗