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Lack of dosing information of the major antibiotics known as oxytetracycline (OTC) for the Pacific white shrimp (Litopenaeus vannamei) could have harmful impact on aquaculture in Thailand. The aim of this study was to detail complete pharmacokinetic information of OTC in the Pacific white shrimp. Sixty-four male L. vannamei weighing 14-22 g with carapace length of 2.30-3.00 cm in the standardized moulting stage of C-D(0) were used for the investigations. Single dose, 10 microg/g body weight OTC solution was administered intra-sinusally (i.s.), and the shrimps were then sampled in three replicates at time intervals of 0.25, 0.5, 2, 4, 6, 9, 12, 24, 48, 72, 170, 336 and 504 h postdose. OTC levels with time intervals in biological matrices including the hemolymph, abdominal muscle, and digestive gland of each sample were determined by validated high-performance liquid chromatography, and were analyzed with noncompartment and compartment models. A simplified two-compartment model was employed rather than a more complicated model, with additional digestive compartment if necessary. A significant portion of the OTC was found in the digestive glands, even though the OTC was administered i.s. The model indicated that the OTC was thus not only distributed into the tissue compartment, but also to the digestive gland, from where it was eliminated from the shrimp's body. The dispositional half-lives of all compartments was found to be 14-21 h. Approximately 60% of the drug elimination took place in digestive gland, which is proposed to be the major route of elimination.

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Abstract. The aim of the study is to examine thermal behavior of water within reticulated structure of bacterial cellulose (BC) films by sub-ambient differential scanning calorimetry (DSC). BC films with different carbon source, either manitol (BC (a)) or glycerol (BC (b)), were produced by Acetobacter xylinum using Hestrin and Shramm culture medium under static condition at 30±0.2°C for 3 days. BC samples were characterized by electron scanning microscopy and X-ray diffraction spectroscopy. The pore analysis was done by B.H.J. nitrogen adsorption. The pre-treated with 100% relative humidity, at 30.0±0.2°C for 7 days samples were subjected to a between 25 and −150°C-cooling-heating cycle of DSC at 5.00°C/min rate. The pre-treated samples were also hydrated by adding 1 μl of water and thermally run with identical conditions. It is observed that cellulose fibrils of BC (a) were thinner and reticulated to form slightly smaller porosity than those of BC (b). They exhibited slightly but non-significantly different crystalline features. The freezable bound water behaved as a water confinement within pores rather than a solvent of polymer which is possible to use thermoporosimetry based on Gibb-Thomson equation to approach pore structure of BC. In comparison with nitrogen adsorption, it was found that thermoporosimetry underestimated the BC porosity, i.e., the mean diameters of 23.0 nm vs. 27.8 nm and 27.9 nm vs. 33.9 nm for BC (a) and BC (b), respectively, by thermoporosimetry vs. B.H.J. nitrogen adsorption. It may be due to large non-freezable water fraction interacting with cellulose, and the validity of pore range based on thermodynamic assumptions of Gibb-Thomson theory.

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