Although the voltage-sensitive Ca channel present in Paramecium has been subjected to detailed physiological and genetic analysis, no organic ligands have been described that block this channel with high affinity and that ultimately can be used to identify channel components. Based on a previous observation that the naphthalene sulfonamide calmodulin antagonist W-7 can block Paramecium Ca channels at high concentration, we have synthesized analogs of W-7 that block these channels at concentrations of <1 aiM. The effectiveness of these compounds was tested both by a sensitive behavioral assay and on Ca channels that had been incorporated into planar lipid bilayers. Despite the fact that these compounds are effective Paramecium calmodulin antagonists, two independent lines of evidence suggest that W-7 and its analogs block the Ca channel by a mechanism that is independent of their action on calmodulin. In addition, the sensitivity to W-7 or dihydropyridines of Ca channels present in a number of eukaryotic phyla has been used to identify similarities in Ca channels from widely diverse organisms. It appears that the pharmacological specificity provides a means to group Ca channels.

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Summary:In this work, we introduce 6-['sFlfluoro-L-m tyrosine (6-FMT) and compare its in-vivo kinetic and bio chemical behaviors in monkeys and rodents with those of 4-FMT and 6-['sFlfluoro-L-3,4-dihydroxyphenylalanine (DOPA) (FDOPA). These radiofluorinated m-tyrosine presynaptic dopaminergic probes, resistant to peripheral 3-0-methylation, offer a nonpharmacologicai alternative to the use of catechol-O-methyltransferase inhibitors. Like FDOPA, 4-FMT and 6-FMT are analogs that essen tially follow the L-DOPA pathway of central metabolism. After i.v. administration in nonhuman primates and ro dents, these new radiofluorinated m-tyrosine analogs ac cumulate selectively in striatal structures and allow for

Diclofop-methyl [methyl 2-[4-(2,4-dichlorophenoxy)phenoxy]propanoate] was hydrolyzed initially to diclofop [ 2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid] in roots of resistant wheat and susceptible oat. Diclofop was detoxified rapidly in wheat roots by aryl hydroxylation of the 2,4dichlorophenyl moiety to at least three isomeric aryl-hydroxylated compounds and conjugation to acidic aryl 0-glycosides. Virtually no diclofop accumulated in wheat roots, but in oat roots, approximately 35% of the radioactivity recovered was phytotoxic diclofop. The primary pathway in oat roots produced a water-soluble metabolite that was identified by mass spectroscopy as a neutral glucose ester conjugate of diclofop. Small quantities of the three hydroxylated isomers of the acidic aryl 0-glycoside were products of a secondary metabolic pathway in oat roots. The ability of wheat roots to detoxify diclofop-methyl completely by aryl hydroxylation and subsequent conjugation is probably the basis for herbicidal selectivity.Diclofop-methyl is a selective herbicide that controls a number of annual grass weeds in cereal crops (Anderson, 1976; Miller and Nalewaja, 1974). Root and shoot growth in oat and wild oat is inhibited by diclofop-methyl, whereas wheat growth is unaffected (Shimabukuro et al., 1978;Hoerauf and Shimabukuro, 1979). Absorption and translocation of diclofop-methyl are not important factors in selectivity (Brezeanu et al., 1976;Shimabukuro et al., 1979;Jacobson and Shimabukuro, 1982). Gorbach et al. (1977) and Shimabukuro et al. (1979) found a water-soluble conjugate in diclofop-methyl-treated wheat shoots that was acid hydrolyzed to ringhydroxylated diclofop. They suggested that the conjugate was an aryl 0-glycoside. In wild oat shoots, the major water-soluble conjugate was hydrolyzed to the free acid, diclofop, suggesting that the conjugate was a neutral glucose ester (Shimabukuro et al., 1979). This difference in metabolism between resistant wheat and susceptible oat suggests that metabolism is the basis for herbicidal selectivity. This report examines the metabolism in diclofop-methyl in roots of resistant wheat and susceptible oat for two reasons: (1) to compare the metabolism in root and shoot tissues of both species and (2) to further characterize and identify the water-soluble metabolites found in both species.

The absorption and translocation of diclofop‐methyl (methyl 2‐[4(2′,4′‐dichlorophenoxy)phenoxy]propanoate) was examined by using a specially designed treatment apparatus that separated excised roots or roots of seedlings into four zones. [14C]‐Diclofop‐methyl was absorbed along the entire root length of both wheat (Triticum aestivum L.) and oat (Avena sativa L.). In both species, absorption was greatest in the apical region of the root. Absorption by the apical region of wheat roots was more than three times greater than the basal portions, and more than twice as great as the apical region of oat roots. Less than 5% of the absorbed diclofop‐methyl was translocated in both wheat and oat roots. Diclofop‐methyl and diclofop(2‐[4(2′,4′‐dichlorophenoxy)phenoxy]propanoic acid) were the predominant translocated forms. The absorption and translocation of amitrole (3‐amino‐1,2,4‐triazole) were also examined. Amitrole was absorbed along the entire length of wheat roots and translocated primatily in the basipetal direction. The usefulness of the specially designed apparatus for biochemical and physiological studies is discussed.