Pubertal exposure to saisentong: Effects on thyroid and hepatic enzyme activity in juvenile female rats

Dissipation and dietary risk assessment of kasugamycin and saisentong in Chinese cabbage

A quick, easy, cheap, effective, rugged, and safe pretreatment method using dispersive solid-phase extraction was developed to quantify kasugamycin in Chinese cabbage samples by using ultra-performance liquid chromatography/tandem mass spectrometry. A pretreatment method involving precolumn transformation was utilized to determine the residue of saisentong in Chinese cabbage through high-performance liquid chromatography/ultraviolet detection. These methods were successfully applied through field trials to determine the contents of kasugamycin and saisentong in Chinese cabbage. The dissipation of kasugamycin and saisentong in Chinese cabbage followed first-order kinetics with a linear correlation coefficient of 0.9066-0.9731 at the 95% confidence level. The half-lives of kasugamycin and saisentong in Chinese cabbage were 1.8-2.0 and 2.2-3.8 days, respectively. Terminal residual levels of kasugamycin in Chinese cabbage were not detected 14 days after application. The dietary risk assessment of kasugamycin and saisentong in Chinese cabbage showed that their risk quotients were 0.93 and 2.58%, respectively, in the preharvest interval (PHI) of 14 days. Kasugamycin and saisentong in Chinese cabbage did not pose potential health hazards at PHI of 14 days. The maximum residue limits of kasugamycin and saisentong in Chinese cabbage were 0.02 and 0.36 mg/kg, respectively, and 14 days was the safe PHI.

Thyroid-disrupting effects and mechanism of thiazole-Zn-induced thyroid cell hypertrophy and hyperplasia in male Sprague-Dawley rats

Thiazole-Zn is a systemic fungicide synthesized and developed in China that has been used for the prevention and treatment of bacterial and fungal diseases on fruits and vegetables. Thiazole-Zn is a new thyroid disruptor chemical. The purpose of this study was to clarify the thyroid-disrupting property of thiazole-Zn and the mechanism responsible for thyroid hormone (TH) biosynthesis inhibition in male rats induced by thiazole-Zn. First, the effects of different thiazole-Zn doses and exposure times on the thyroid weights, thyroid morphology and serum hormone levels of rats were investigated. The results showed that thiazole-Zn increased thyroid weights and serum thyroid-stimulating hormone (TSH) levels and induced thyroid cell hypertrophy and hyperplasia in a dose-related and time-related manner. Furthermore, measurement of thyroid radioiodine uptake in vivo in rats confirmed that thiazole-Zn inhibited active iodide uptake into the thyroid, which reduced circulating levels of serum T3 and T4. Decreases in circulating THs resulted in a compensatory increase in serum TSH levels through a negative feedback system. Subsequently, sustained excessive stimulation of the thyroid gland by TSH led to thyroid follicular cell hypertrophy and hyperplasia. In addition, thiazole-Zn increased sodium/iodide symporter (NIS) expression in the rat thyroid, and the increased NIS expression promoted and restored iodide uptake into the thyroids of rats. The risk of iodine intake inhibition by thiazole-Zn to humans, especially susceptible individuals, such as children and pregnant women, warrants additional attention.

Dissipation and translocation of saisenxin in tobacco and soil under conventional field and controlled laboratory conditions

The aim of this investigation was to investigate the fate and translocation characteristics of saisenxin (SSX), a novel organic zinc fungicide, in the environment and tobacco plants under conventional field and laboratory conditions. A rapid and sensitive analytical technique based on high-performance liquid chromatography was used for determination of SSX, in soil samples and tobacco leaf, stem and root samples. The method had satisfactiry linearity (R2 = 0.9999) and the limits of detection and of quantitation of the target compound were 0.06 and 0.20 mg kg-1, respectively. The average recoveries were in the range of 89.74-94.24% in soil, leaf, stem and root samples, with relative standard deviations of <8%. For conventional field trials, the half-life (t1/2) of SSX was 5.9-6.5 days in soil and 4.8-5.3 days in tobacco leaves; the corresponding values under controlled laboratory conditions were extended to 7.1 and 7.6 days. The translocation factor (TF) values were in the range of 0-2.25 and 0-0.25 for foliage and root irrigation treatments, respectively. The TFs of SSX in tobacco indicated that tobacco had a high ability to transfer SSX upward.