Neomycin metabolism in calves.

Disposition of oral neomycin in calves was determined using 14C-labeled neomycin. The influences of age, diet, and method of administration were observed. All calves were killed 96 h after a single oral dose of [14C]neomycin (approximately 30 mg/kg) and the distribution of 14C in excreta and tissues was determined.

Evidence for involvement of non-biliary excretion into the intestines in the formation of methylsulphonyl-containing metabolites of 2-chloro-N-isopropylacetanilide (propachlor) by swine and rats.

1. Radiolabelled metabolites excreted in the urine of swine after an oral dose of 14C-propachlor were similar to those previously reported with rats and included methylsulphonyl (CH3SO2-)-containing metabolites. 2.

Mass spectra of aniline glucuronides.

Mass spectra of TMS derivatives of aniline glucuronide and pentachloroaniline glucuronide are presented, and the fragmentation of these derivatives is compared with that of TMS aryl-O-glucuronides. Fragmentation yielding ions entirely from the glycone moiety was sufficiently similar to establish these N-glucuronides as TMS glucuronides in the same manner used for TMS-O-glucuronides; however, differences observed may be diagnostic for TMS-N-glucuronides.

Carbon-14-labeled diethylstilbestrol synthesis by the McMurry method: concurrent formation of hexestrol.

Isotopically labeled diethylstilbestrol prepared from p-methoxypropiophenone by coupling with TiCl3-LiA1H4 contained approximately 50% hexestrol. Nonlabeled preparations and a subsequent labeled preparation had less than 2% hexestrol in them. Initial examinations for purity by gas-liquid chromatography, thin-layer chromatography, and isotope dilution did not show the presence of hexestrol.

Diethylstilbestrol metabolism in food-producing animals.

The metabolic fate of diethylstilbestrol (DES) in food-producing animals is described in this paper. Emphasis is on ruminant animals because DES is currently used in their production. Data presented from recent studies in ruminants show 14C excretion (rates and routes) and distribution after ingestion or subcutaneous implantation of 14C-labeled DES.