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It is not the total but the (bio)accessible concentration of veterinary medicines that determines their toxicity in the environment. We elucidate the changes in (bio)accessibility of manure-applied sulfadiazine (SDZ) with increasing contact time in soil. Fattening pigs were medicated with 14C-labeled SDZ, and the contaminated manure (fresh and aged) was amended to 2 soil types (Cambisol, Luvisol) and incubated for 218 days at 10 degrees C in the dark. Antibiotic residues of different bioaccessibility were approached by sequential extractions with 0.01 M CaCl2 (CaCl2 fraction), methanol (MeOH fraction), and finally acetonitrile/water (residual fraction, microwave extraction at 150 degrees C). In each fraction, total radioactivity, SDZ, and its major metabolites were quantified. The results showed that both SDZ and,to a lesser extent 4-hydroxysulfadiazine (4-OH-SDZ) were rapidly reformed from N-acetylsulfadiazine (N-ac-SDZ) during the first 2-4 weeks after fresh manure application, i.e., the N-acetylated metabolite does not sequester in soil to a significant extent Yet, the water and methanol extractable SDZ and 4-OH-SDZ also dissipated rapidly (DT50 = 6.0-32 days) for the fresh manure treatment with similar rate constants for both soil types. In the residual fractions, however, the concentrations of both compounds increased with time. We conclude that the residual fraction comprises the sequestered pool of SDZ and its hydroxylated metabolite. There they are entrapped and may persist in soil for several years. Including the residual fraction into fate studies thus yields dissipation half-lives of SDZ which exceed those previously reported for sulfonamides by a factor of about 100.

The bis(L-histidine)ZnCl, complex 1 is likely to have tetrahe-histidine derivative N"-acetylhistidine the complexes (Acdral ZnN,Cl, coordination. For the compound @-histidine)-His)ZnX . H,O (5, X = C104, BF4) have been isolated which ZnCl, . HCl (2) a structure determination has revealed a tetra-are coordination polymers in the solid state. From pH-dehedral ZnOC1, coordination. Of the C-protected histidine de-pendent 13C-NMR studies it is concluced that in solution the rivatives His-OMe and His-NH, and zinc salts of non-imidazole N and carboxyl 0 are coordinated to zinc in (Accoordinating anions the complexes (His-OMe),ZnXz (3) and His)Zn and (Ac-His),Zn units. The doubly protected histidine (His-NH,),Zn(C10,)2 (4) were obtained. A structure determi-derivative Bz-His-OMe acts as a monodentate ligand forming nation of (His-OMe),Zn(BPh,), . H 2 0 has revealed a ZnN4 co-the tetrahedral complexes (Bz-Hi~-0Me)~Zn(C10~), (6) and ordination with chelating histidine units. Of the N-protected [(Bz-His-OMe),Zn(2,9-dimethyl-o-phenanthroline)](C~O4)~ (7).

An efficient extraction of sulfadiazine residues from soils is difficult, as sulfadiazine is known to form quickly sequestering residues. The objective of this study was to optimize an exhaustive extraction for aged residues of sulfadiazine and its two major metabolites, N-acetylsulfadiazine and 4-hydroxysulfadiazine, from soil. For this purpose two representative used agricultural soils (Luvisol, Cambisol) were blended with manure derived from [(14)C]sulfadiazine-treated pigs and incubated at 10 degrees C in the laboratory. After different extraction tests with various solvent mixtures (two- to four-component mixtures with water, methanol, acetonitrile, acetone, and/or ethyl acetate), different pH values (pH 4 and 9), and extraction temperatures (up to 200 degrees C), soil extracts were measured by liquid scintillation counting and liquid chromatography coupled to tandem mass spectrometry. With respect to sulfadiazine yields, stability of soil extracts, and the amount of coextracted matrix, a microwave extraction of soil (15 min, 150 degrees C) using acetonitrile/water 1:4 (v/v) is the method of choice for the exhaustive extraction of aged sulfadiazine residues from soils.

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Adolescents with externalizing behaviors are at risk for multiple social and health impairments that may persist into adulthood. Although empirically supported treatments are available for teenagers with severe externalizing behavior and their families, only a few parenting programs have been evaluated for adolescents with subclinical levels of behavior problems. In the present randomized controlled trial (N = 75), we examined the feasibility and efficacy of the Parent-Web, a new Internet-based parenting program for parents of teenagers. Participants reported high satisfaction with the program, 74% completed all five modules and dropout was only 14%. Generalized linear mixed models showed short-term (8 weeks) improvements in parent-reported teenager externalizing behaviors, family conflicts, and family warmth compared to a waitlist control condition. Receiving the Parent-Web was also associated with more improvements in parent-reported teenage emotional symptoms and peer problems, as well as parental stress and depression. No differences regarding parenting behaviors between the two groups were found. Those in the intervention group maintained their posttreatment gains on primary outcomes at the follow-up assessment, 6- to 9-months after the program. Although limited by relying solely on parent report, and by a relatively small sample size, we conclude that our study contributes some preliminary evidence for the utility of supporting parents of adolescents at risk of developing behavior problems through an Internet-based intervention.