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Biomedical subjects

J B Shields

Publications and source records attributed to J B Shields.

60 records · Page 4Linked to original sources

CT characteristics of aortic atherosclerotic aneurysm versus aortic dissection.

In an attempt to better define criteria for the diagnosis of atherosclerotic aneurysm (AA) and aortic dissection (AD) using CT the scans of 60 documented aortic lesions were reviewed. Hyperdensity of the aortic wall at multiple levels was found to be specific for AD. Central displacement of atheromatous calcification and deformity of the residual aortic lumen were more common in AD than in AA. Peripheral location of aortic wall calcification and a round aortic lumen in cross section were more common in AA than in AD. Central calcification in AA appeared to be associated with a serious short-term prognosis in several cases. A thickened aortic wall of low density was more common in AA than in acute AD, but this relationship was not significant when acute and chronic ADs were considered as a single group. Wall thickness correlated with cross-sectional size of the aortic lesion in AA but not in AD. The mean maximum wall thickness exceeded 1 cm for both AA and AD and was not significantly different between the two; contrary statements have been made in the angiographic literature.

Aortic Dissection↗

Determination of fluazifop-butyl and fluazifop acid in soybeans and soybean oil using liquid chromatography with oxidative amperometric detection.

A new method is described for the determination of the herbicide fluazifop-butyl, and its metabolite fluazifop acid, in soybeans and soybean oil as fluazifop acid. Liquid chromatography with amperometric detection (LC/AD) is used to determine fluazifop acid produced from the metabolism or base hydrolysis of fluazifop-butyl in soybeans and soybean oil. These foods were spiked with fluazifopbutyl at 0.05, 0.10, and 0.50 ppm and hydrolyzed with 0.2N NaOH in methanol. The hydrolysate (adjusted to pH less than or equal to 1) is extracted with dichloromethane and the extract is washed with 1.0% NaHCO3. The NaHCO3 is acidified to pH less than or equal to 1 and extracted with dichloromethane; the partitioning is repeated 2 more times. The dichloromethane is removed, mobile phase solvent is added, and aliquots are injected onto a PRP-1 liquid chromatographic column; fluazifop acid is separated from coextracted compounds and detected at an applied potential of + 1.25 V, using an amperometric electrochemical detector in the oxidation mode. Recoveries ranged from 69 +/- 6.5 to 101 +/- 18% and from 72 +/- 7.5 to 88 +/- 11% for soybeans and soybean oil, respectively. Accuracy of these recoveries was confirmed by use of 14C-radiolabeled fluazifop-butyl and by liquid scintillation spectrometry of the 14C-fluazifop acid released.

Chemical Phenomena↗

Determination of naptalam and its metabolite in foods, as 1-naphthylamine, using liquid chromatography with oxidative electrochemical detection.

A new method is described for the determination of the herbicide naptalam and its metabolite 1-naphthylamine in several foods. The method is sensitive, selective, and extremely rapid compared with previously reported methods. Liquid chromatography with electrochemical detection (LC/ECD) is used to determine 1-naphthylamine produced from the metabolism or base hydrolysis of naptalam in asparagus, peaches, and cranberries. These foods were spiked with naptalam at 0.05 and 0.11 ppm and hydrolyzed with 30% NaOH with concomitant distillation of 1-naphthylamine. Aliquots of the distillate were injected onto a reverse-phase PRP-1 LC column for separation of 1-naphthylamine from coextractives near the solvent front and detection at an applied potential of +0.83 V using an amperometric electrochemical detector in the oxidation mode. Recoveries ranged from 89% +/- 2% to 97% +/- 8% for all foods at both spiking levels. Accuracy of these recoveries was confirmed by use of 14C-radiolabeled naptalam and radioassay by liquid scintillation spectrometry of the 14C-1-naphthylamine released.

1-Naphthylamine↗

Determination of total free and glucose-conjugated 3-phenoxybenzyl alcohol residues in foods by gas chromatography with electron capture detection.

A method was developed to determine the combined amounts of residual, free 3-phenoxybenzyl alcohol (permethrin alcohol) and its acetone-extractable glucosides in representative fruits and vegetables after application of pyrethyroid insecticides such as permethrin or cypermethrin. 3-Phenoxybenzyl glucoside was synthesized and used to spike food samples. Conditions were developed for extraction, enzymatic hydrolysis, derivatization with heptafluorobutyric anhydride, and cleanup prior to detection and quantitation by gas chromatography with electron capture detection. Limits of detection in various foods were < or = 0.01 ppm. In addition, 2 sets of field trial samples that were sprayed with permethrin and collected at intervals were also analyzed. In general, the amounts of total permethrin alcohol in foods were small.

Aerosols↗