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L J Schmidt

Publications and source records attributed to L J Schmidt.

21 records · Page 2Linked to original sources

Liquid chromatographic determination of para-toluenesulfonamide in edible fillet tissues from three species of fish.

Chloramine-T (N-sodium-N-chloro-p-toluene-sulfonamide) is a candidate therapeutic drug for treating bacterial gill disease, a predominant disease of a variety of fish species. Research has been initiated to obtain the U.S. Food and Drug Administration's (FDA) approval for the use of chloramine-T on a variety of fish species. An attribute of a therapeutic aquaculture drug that must be characterized before the FDA approves its use is depletion of the drug's marker residue (the drug's parent compound or metabolite of highest concentration in an edible tissue). para-Toluenesulfonamide (p-TSA) is the primary degradation product and marker residue for chloramine-T in rainbow trout. To conduct residue depletion studies for chloramine-T in fish, a robust analytical method sensitive and specific for p-TSA residues in edible fillet tissue from a variety of fish was required. Homogenized fillet tissues from rainbow trout (Oncorhynchus mykiss), walleye (Stizostedion vitreum), and channel catfish (Ictalurus punctatus) were fortified at nominal p-TSA concentrations of 17, 67, 200, 333, and 1000 ng/g. Samples were analyzed by isocratic reversed-phase liquid chromatography (LC) with absorbance detection at 226 nm. Mean recoveries of p-TSA ranged from 77 to 93.17%; relative standard deviations ranged from 1.5 to 14%; method quantitation limits ranged from 13 to 18 ng/g; and method detection limits ranged from 3.8 to 5.2 ng/g. The LC parameters produced p-TSA peaks without coelution of endogenous compounds and excluded chromatographic interference from at least 20 chemicals and drugs of potential use in aquaculture.

Animals↗

Characterization of a TPA-response element in the 5'-flanking region of the androgen receptor gene.

The androgen receptor (AR) protein is an important transacting factor that is necessary for mediating gene expression of androgen-responsive genes. The expression of the AR gene is regulated by androgens and agents that utilize the calcium, protein kinase A, and protein kinase C pathways. Although the role of the calcium and protein kinase A pathways in the regulation of the AR gene has been investigated, the mechanism of regulation of AR through the protein kinase C pathway is not known. We have isolated the 5'-flanking region of the mouse AR gene and identified a consensus TPA (12-O-tetradecanoylphorbol 13-acetate)-response element (TRE). Transient transfection assays indicate that the TRE sequence is sufficient to confer TPA responsiveness to cells treated with TPA. Gel retardation assays and DNA footprint analysis demonstrated specific binding of the TRE and protection of the TRE sequence. Thus, these results describe a TRE in the 5'-flanking region of the AR gene and demonstrate that the TRE is responsive to TPA treatment.

Animals↗