Pharmacokinetics,optimal dosages and withdrawal time of florfenicol in Asian seabass (Lates calcarifer) after oral administration via medicated feed

Asian seabass (Lates calcarifer) is an economically important fish in Asian and Australian markets, but few pharmacokinetic (PK) data of antimicrobial drugs in this species is available. The present study investigated the PK behaviour of florfenicol (FF) through medicated feed in Asian seabass cultured at 25°C. The serum and muscle/skin concentrations of FF and its metabolite florfenicol amine (FFA) were determined by the HPLC-FLD method and analysed by one-compartmental model. The optimal dosages were determined by pharmacokinetic-pharmacodynamic (PK-PD) approach and the linear regression analysis was used to determine the withdrawal time (WDT). The PK study following a single oral administration of 15 mg/kg FF via medicated feed revealed that the absorption half-life (t_1/2Ka), elimination half-life (t_1/2K), peak concentration (C_max), area under the concentration-time curve (AUC), volume of distribution (Vd/F) and clearance (CL/F) were 1.47 h, 8.07 h, 8.61 μg/ml, 146.41 h·μg/ml, 1.19 L/kg and 0.102 L/kg/h, respectively. The muscle/skin concentration-time profile was similar to that of the serum, suggesting well distribution but only a small fraction of FF was metabolized to FFA. The optimal dosage for a minimum inhibitory concentration of 2 μg/ml was calculated as 13.38 mg/kg/day. The appropriate WDT after multiple oral medications with 15 mg/kg FF once daily for 7 days was determined as 8 days. Information obtained from the current study can potentially be applied for the treatment of bacterial diseases in farming Asian seabass.     

Morphological and Anatomical Assessment of KDML 105 (Oryza sativa L.spp.indica) and Its Mutants Induced by Low-Energy Ion Beam

Thai jasmine rice KDML 105 is consumed around the world.BKOS,PKOS and TKOS are new cultivars produced from low-energy ion beam induction in KDML 105.The purpose of this study is to compare the morphology and anatomy between KDML 105 and the three new cultivars.Seeds of the four cultivars were germinated and grown in pots until flowering phase.The plants’ organs were observed and the lengths of culms,ligules,leaves and panicles were measured.Leaf surface area was calculated and numbers of roots,spikelets and tillers were counted.BKOS and PKOS had significantly shorter culms than KDML 105 and TKOS.The largest leaf area was found in KDML 105 followed by TKOS,BKOS and PKOS,respectively.Numbers of roots and tillers in BKOS and TKOS were significantly fewer than those in KDML 105 and PKOS.The number of spikelets per plant in BKOS was the lowest among all cultivars.For anatomical comparison,cross sections of culms and roots were observed.All plants had a similar arrangement of tissues,but the number and size of cells were different.Furthermore,longitudinal sections of culms showed that the lengths of epidermal and parenchyma cells were directly related with the length of the culm.To compare the leaves,both stomata and epidermal cells were counted and the lengths of the guard cells were measured.The lengths of guard cells of BKOS and PKOS were shorter,but the stomatal density and the stomatal index were significantly greater than those of KDML 105.For TKOS,though the length of guard cells was shorter than that in KDML 105,the difference was not significant.However,the stomatal density and stomatal index were significantly higher than those in KDML 105.