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Biomedical subjects

D J Ecobichon

Publications and source records attributed to D J Ecobichon.

93 records · Page 6Linked to original sources
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Abiotic transformations and decomposition kinetics of 4-carbamoyl-2'-[(hydroxyimino)methyl]-1,1'-(oxydimethylene)-bis(pyridin ium chloride) in aqueous phosphate buffers.

The rate of disappearance of 4-carbamoyl-2'-[(hydroxyimino)methyl]-1,1'-(oxydimethylene) bis (pyridinium chloride) (HI-6) from aqueous phosphate buffers (pH 3.0-9.1) was both pH and temperature sensitive. In midrange buffers (pH 6.0-9.1, mu = 0.2 M) at 37, 25, or 4 degrees C the decomposition followed first-order kinetics consistent with hydroxide-promoted decomposition of the un-ionized drug or with hydrolysis of the ionized oxime anion to result in 4-carbamoyl-2'-hydroxy-1,1'-(oxydimethylene)bis(pyridinium) cation (intermediate 1). The subsequent conversion of intermediate 1 to 4-carboxy-2'-hydroxy-1,1'-(oxydimethylene)bis(pyridinium) cation (intermediate 2) followed higher order kinetics which were consistent with either acid- or base-promoted hydrolysis of the B-ring amide functionality. After approximately 138 days in the dark, the sum of the residual HI-6, intermediate 1, and intermediate 2 in the crude decomposition mixture accounted for 89.9 +/- 10.0% of the initial substrate. Minor byproducts included 4-carbamoyl-2'-carboxy-1,1'-(oxydimethylene)bis(pyridinium) cation, 2-pyridinealdoxime, 2-pyridinecarboxaldehyde, 2-hydroxypyridine, isonicotinamide, isonicotinic acid, and traces of cyanide. In addition, 2-cyanopyridine appeared to be a transient intermediate in more alkaline media. In total, this drug resembles other mono- and bis(pyridinium) aldoximes in terms of the decomposition routes in aqueous solutions at intermediate pHs.

Antidotes↗
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Our changing perspectives on benefits and risks of pesticides: a historical overview.

The introduction of chemical pesticides following WW II ushered in the era of the "quick fix" for any aqricultural, forestry and human health problems. Scenarios of use, misuse, abuse and environmental contamination can be presented for any class of pesticide, culminating in dependence on these chemicals for increased production of food and fibre and improved health. With time, sophisticated agents having unique, target-specific mechanisms of action evolved but at increased cost(s) to crop production. Equatorial countries, rapidly becoming "breadbaskets" of the world, are particularly dependent on pesticides as they strive to increase production of nontraditional export products (NTEPS), valuable cash crops in demand in countries having more temperate climates. Developing nations have neither the legislation and regulations necessary to control pesticides nor trained personnel to inspect and monitor use, to analyze residues in produce or to initiate training programs. Their transition from agrarian to industrialized societies has meant that smaller, less well educated populations must shoulder the responsibility of increased traditional food production for consumption by urban populations as well as that of NTEPS. Unfortunately, to attain these goals, many older, more toxic, environmentally persistent and cheap pesticides, long banned in developed countries, are used extensively, creating serious local and global contamination and health problems.

Animals↗