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Biomedical subjects

J F Armstrong

Publications and source records attributed to J F Armstrong.

33 records · Page 2Linked to original sources
PubMed1975

Exposure of apple thinners to parathion residues.

In studies of potential exposure of a volunteer working under controlled conditions during apple hand-thinning operations at 1, 24, 48, 72, 96, 168, and 240 hr after application of conventional 0.03% parathion spray, both dermal and respiratory exposure values were greater where water-wettable powder formulations were used than where emulsifiables were used. Residue levels of parathion on leaves from the two types of applications were about the same. Only trace amounts of paraoxon could be detected at one and seven days after application. Highest exposure values (14.2 mg/hr dermally and 0.15 mg/hr respiratorily) were obtained within 24 hr of application. Exposure was considerably less after residues were 72 hr old. Greatest exposure was on the forearms and hands. Urinary p-nitrophenol excretion indicated slightly more absorption following exposure in water-wettable powder experimental plots. Potential exposure values indicate that absorption could reach hazardous levels after one or two hr of work, even at the 96-hr residue period, if all the pesticide were absorbed. Considering that only a small fraction of the total amount would be absorbed, it is calculated that at 75-hr residue period poisoning should not occur. There was no significant change in blood cholinesterase activity of the volunteer worker. Variation in spray deposit within an orchard due to poor tank mixing did not appear to be great enough to be considered an important factor affecting exposure.

Administration, Topical↗
PubMedDate not supplied

Determination of N-nitrosodimethylamine levels in some Canadian 2,4-D amine formulations.

Levels of N-nitrosodimethylamine (NDMA) were determined in 112 samples of 2,4-dichlorophenoxyacetic acid, (2,4-D), formulated as the dimethylamine salt, collected over a 2 year period from products on the Canadian market. A sample aliquot is partitioned with dichloromethane, and the co-extracted dimethylamine is removed by cleanup on a silica gel column. The eluates containing NDMA are concentrated, an internal standard of N-nitrosodipropylamine is added, and nitrosamine levels are determined using a gas chromatograph interfaced with a thermal energy analyzer. Recoveries of NDMA and N-nitrosodiethylamine spiked into samples were 103 +/- 16 and 96.3 +/- 9.8%, respectively. Of the 112 samples analyzed, 92 were below 1 part per million (ppm) relative to the amount of 2,4-D in the samples, 16 were between 1 and 5 ppm, and 4 were greater than 5 ppm. The gas chromatographic column used is compared to a conventional packing material for volatile nitrosamine analysis. Formation of NDMA during cleanup and analysis was shown not to occur.

2,4-Dichlorophenoxyacetic Acid↗
PubMedDate not supplied

Embryonic kidney rudiments grown in adult mice fail to mimic the Wilms' phenotype, but show strain-specific morphogenesis.

12.5- to 14.5-day mouse embryonic kidney fragments were grown syngeneically under kidney or testis capsules in 3 mouse strains for 5-26 weeks to reproduce the Wilms' tumour (WT) phenotype previously reported. About 65% of the transplants grew, but none showed true WT morphology, invaded local tissue or developed metastases. In Swiss mice, most growths contained disorganized stromal and blast cells, but also had more mature structures. CBA growths had cysts, differentiated nephrons and glomeruli, while 129/SV growths gave both types of morphology. In situ mRNA hybridization using the Wilms' tumour predisposition gene (WT1) showed that, unlike the initial rudiments and WT, expression was limited to the glomeruli. The unexpected absence of expression by the apparent blast cells in the growths implies that the system is not a model for WT.

Animals↗