[Simultaneous determination of 31 banned veterinary drugs during egg-laying period in poultry eggs by ultra performance liquid chromatography-tandem mass spectrometry].

The consumption of poultry eggs has increased in recent years owing to the abundance of production and improvements in living standards. Thus, the safety requirements of poultry eggs have gradually increased. At present, few reports on analytical methods to determine banned veterinary drugs during egg-laying period in poultry eggs have been published. Therefore, establishing high-throughput and efficient screening methods to monitor banned veterinary drugs during egg-laying period is imperative. In this study, an analytical method based on ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) combined with QuEChERS-based techniques was developed for the simultaneous determination of 31 banned veterinary drugs encompassing nine drug classes (macrolides, antipyretic and analgesic drugs, sulfonamides, antibacterial synergists, anticoccidials, antinematodes, quinolones, tetracyclines, amphenicols) in different types of poultry eggs. The main factors affecting the response, recovery, and sensitivity of the method, such as the extraction solvent, purification adsorbent, LC separation conditions, and MS/MS parameters, were optimized during sample pretreatment and instrumental analysis. The 31 veterinary drug residues in 2.00 g eggs were extracted with 2 mL of 0.1 mol/L ethylene diamine tetraacetic acid disodium solution and 8 mL 3% acetic acid acetonitrile solution, and salted out with 2 g of sodium chloride. After centrifugation, 5 mL of the supernatant was cleaned-up using the QuEChERS method with 100 mg of octadecylsilane-bonded silica gel (C18), 50 mg of N-propylethylenediamine (PSA), and 50 mg of NH2-based sorbents. After nitrogen blowing and redissolution, the 31 target analytes were separated on a Waters CORTECS UPLC C18 analytical chromatographic column (150 mm×2.1 mm, 1.8 µm) at a flow rate, column temperature, and injection volume of 0.4 mL/min, 30 ℃, and 5 µL, respectively. Among these analytes, 26 analytes were acquired in dynamic multiple reaction monitoring (MRM) mode under positive electrospray ionization (ESI+) conditions using (A) 5 mmol/L ammonium acetate (pH 4.5) and (B) acetonitrile as mobile phases. The gradient elution program was as follows: 0-2.0 min, 12%B-30%B; 2.0-7.5 min, 30%B-50%B; 7.5-10.0 min, 50%B; 10.0-10.1 min, 50%B-100%B; 10.1-12.0 min, 100%B; 12.0-12.1 min, 100%B-12%B; The five other target analytes were acquired in MRM mode under negative electrospray ionization (ESI-) conditions using (A) H2O and (B) acetonitrile as mobile phases. The gradient elution program was as follows: 0-2.0 min, 12%B-40%B; 2.0-6.0 min, 40%B-80%B; 6.0-6.1 min, 80%B-100%B; 6.1-8.0 min, 100%B; 8.0-8.1 min, 100%B-12%B. Matrix-matched external standard calibration was used for quantification. The results showed that all the compounds had good linear relationships within their respective ranges, with correlation coefficients of >0.99. The limits of detection (LODs) and quantitation (LOQs) were 0.3-3.0 µg/kg and 1.0-10.0 µg/kg, respectively. The average recoveries of the 31 banned veterinary drugs spiked at three levels (LOQ, maximum residue limit (MRL), and 2MRL) in poultry eggs ranged from 61.2% to 105.7%, and the relative standard deviations (RSDs) ranged from 1.8% to 17.6%. The developed method was used to detect and analyze banned veterinary drugs in 30 commercial poultry egg samples, including 20 eggs, 5 duck eggs, and 5 goose eggs. Enrofloxacin was detected in one egg with a content of 12.3 µg/kg. The proposed method is simple, economical, practical, and capable of the simultaneous determination of multiple classes of banned veterinary drugs in poultry eggs.

Elevated lactate dehydrogenase predicts poor prognosis of acute ischemic stroke.

BACKGROUND: Lactate dehydrogenase (LDH) is associated with the prognosis of many diseases, but the relationship between LDH and the poor prognosis (recurrence and death) of acute ischemic stroke (AIS) has not been fully clarified. This study aimed to investigate the association between admission LDH level and poor prognosis in patients with AIS. METHODS: This retrospective study enrolled AIS patients treated in Taizhou Hospital of Zhejiang Province from July 2019 to December 2019. Poor prognosis included AIS recurrence and all-cause death at 3, 6, and 18 months. The correction between LDH and poor prognosis or all-cause death was assessed. Lasso Cox expression and multivariate Cox expression analyses were used to evaluate the association of LDH with the risk of poor prognosis and all-cause death, respectively. A nomogram was constructed to evaluate the predictive Values of LDH for the poor prognosis and all-cause death of AIS. RESULTS: 732 patients were included in the study. Multivariate analysis shows that admission LDH levels were significantly correlated with poor prognosis [odds ratio (OR),1.003; 95% confidence interval (95% CI), 1.001-1.005; P = 0.001] and all-cause death (OR, 1.005; 95% CI, 1.000-1.009; P = 0.031). The correlation analysis showed that admission LDH level was positively correlated with National Institutes of Health Stroke Scale (NIHSS) score and modified Rankin Scale (mRS) score. Time-dependent receiver operating characteristic (td-ROC) curves analysis showed that the AUC values of admission LDH level for predicting prognosis of AIS patients in 3-month, 6-month, 12-month and 18-month were 0.706 (95% CI, 0.604-0.810), 0.653 (95% CI, 0.583-0.723), 0.616 (95% CI, 0.556-60676) and 0.610 (95% CI, 0.552-0.680), respectively. And td-ROC also showed that the AUC values of admission LDH level for predicting all-cause death of AIS patients in 3-month, 6-month,12-month and 18-month were 0.861 (95% CI, 0.764-0.958), 0.824 (95% CI, 0.753-0.890), 0.726 (95% CI, 0.633-0.819) and 0.715 (95% CI, 0.622-0.807), respectively. The nomograms were constructed to create the predictive models of the poor prognosis and all-cause death of AIS. CONCLUSION: Higher LDH levels are independently associated with poor prognosis and all-cause death of AIS.

[Appropriate soil nitrate N content for a winter wheat/summer maize rotation system in North China Plain].

A field experiment with 12-level N fertilization in winter wheat growth season and zero-N in summer maize growth season was conducted to study the appropriate soil nitrate N content for a winter wheat/summer maize rotation system in North China Plain. The results showed that when the soil mineral N content before sowing was higher, a split application of 150 kg N x hm(-2) in winter wheat growth season could meet the N demand of both winter wheat and summer maize in the rotation system. The N use efficiency of winter wheat in different N treatments was only from 11% to 23%, while the residual N use efficiency of summer maize ranged from 30% to 52%. When the nitrate N content in top 90 cm soil layer before maize sowing was up to 82 and 151 kg x hm(-2), respectively, the N demand of summer maize at its ten-leaf stage and in its whole growth season could be met with no N application. However, when the nitrate N content in top 90 cm soil layer was less than 46 and 65 kg x hm(-2) at maize ten-leaf stage and after harvest, respectively, no N application could impact maize growth, and decrease its grain yield. With the maize yield and environmental protection considered comprehensively, the nitrate N content in top 90 cm soil layer should be maintained at an appropriate level from 65 to 151 kg x hm(-2) during maize growth season.