β- N-Acetyl- D-glucosaminidase ( NAGase, EC3.2.1.52) is a composition of the chitinases and cooperates with endo-chitinase and exo-chitinase to disintegrate chitin into N-acetylglucosamine. Pacific White Shrimp (P. vannamei) NAGase is involved in digestion and molting processes. Some pollutants in seawater affect the enzyme activity causing loss of the biological function of the enzyme, which affects the exuviating shell and threatens the survival of the animal. The effects of acetic anhydride on the enzyme activity for the hydrolysis of pNP-NAG have been studied. The results show that acetic anhydride can lead to reversible non-competitive inhibition at appropriate concentrations, and the IC50 is estimated to be 9.0 mmol/L. The equilibrium constants have been determined for acetic anhydride binding with the enzyme and/or the enzymesubstrate complexes. Inhibition kinetics of acetic anhydride on the enzyme has been studied using the kinetic method of the substrate reaction. The results suggest that at pH 6.2, the action of acetic anhydride on the enzyme is first quick equilibrium binding and then slow inhibition. The microscopic rate constants have been determined for inhibition and reactivation. The results show that k + 0 is much larger than k - 0, indicating the enzyme is completely inactivated at sufficiently large modificator concentration.

Objective To establish the standards for classification of urinary fistula after kidney transplantation. Methods From December 1993 to February 2009, 1313 cases of renal transplanta-tions were operated, out of which 102 cases of urinary fistulas occurred (7.8%). Based on the princi-ple of the urethral injury classification method, we divide urinary fistula into simple and complex clas-ses by the cause, location, and the severity of the disease. Results There were 81 cases (79.4%) of simple urinary fistulas, of those 76 cases were ureteral end necrosis,4 cases were due to ureter blad-der anastomosis suture,1 case was anastomotic problem caused by wound infection. There were 21 ca-ses(20.6%) of complex urinary fistulas, of these 2 cases had fistulas at renal pelvis, 11 cases at ure-ter-bladder interface and 6 cases had ureteral necrosis longer than 2 cm. For the 81 cases urinary fistu-las patients, 34 patients conservative treatments were cured and 47 patients need surgeries. For all complex urinary fistulas need surgeries: 11 cases had surgery once, 5 cases had 2 times, 3 cases had 3 times and 2 cases had 4 times. Among the 2 groups, three patients (2.9%) died of urinary fistulas which led to severe lung infection. Conclusions A "Five Steps Procedure" could be used for diagno-sis and treatment of post renal transplantation fistula. The urinary fistulas are divided into simple and complex types after renal transplantation. This provides a guidance for the best choice of treatment.

1 313 patients who received renal transplantations at Department of Urology, Research Institute of Field Surgery, Daping Hospital, Third Military Medical University of Chinese PLA from December 1993 to October 2008 were selected in the experiment. Urinary fistula occurred in 68 patients of them after renal transplantation. In order to make diagnosis more standard, 68 patients was classified in accordance with diagnostic classification standards after renal transplantation. The 68 patients were divided into simple and complex urinary fistulas in accordance with lesion degree. They were divided into low, high and multiple fistulas in accordance with the position and etiology. 47 (69.1%) of 68 cases were simple urinary fistulas: 42 cases were because of terminal ureteral necrosis; 4 cases were because the anastomosis was mended unsuitably; 1 case was because of poor healing of anastomosis due to infections. 21(30.9 %) cases were complex urinary fistulas. The position of orificium fistula: orificium fistula located at renal pelvis, ureter and anastomosis were 2, 2 and 11 cases, respectively. 6 cases had ureteral necrosis longer than 2 cm. The times of repair: 11 cases had 1 time, 5 cases had 3 times, 3 cases had 3 times and 2 cases had 4 times. 2 cases (2.9%) died because of severe pulmonary infection caused by urinary fistula. Result suggests that there are two advantages of dividing urinary fistula into the simple and complex types after renal transplantation: one is that the diagnosis of urinary fistula is more carefully and standardized, and the other is that doctors can make the best choice for treatment in order to get the best efficacy.

Objective:To construct the prediction model of death risk of Stanford type A aortic dissection (AAD) based on Cox proportional risk regression model.Methods:AAD patients who were diagnosed and received surgical treatment admitted to the department of cardiothoracic surgery of Tongji Hospital, Tongji Medical College of Huazhong University of Science and Technology from January 1st, 2019 to April 30th, 2020 were enrolled. The general situation, clinical manifestations, pre-hospital data, laboratory examination and imaging examination results of the patients were collected. The observation period was up to the death of the patients or ended on April 30th, 2021. They were divided into the model group and the verification group according to the ratio of 7∶3. Lasso method was used to screen prognostic variables from the data of the modeling group, and multivariate Cox regression analysis was included to construct the AAD death risk prediction model, which was displayed by nomogram. The receiver operator characteristic curve (ROC curve) was used to evaluate the discrimination of the model, the calibration curve to evaluate the accuracy of the model, and the clinical decision curve (DCA) to evaluate the effectiveness of the model.Results:A totel of 454 patients with AAD were finally included, and the mortality was 19.4% (88/454). Lasso regression analysis was used to screen out 10 variables from the data of 317 patients in the model group, and the prediction model of death risk was constructed: 0.511×abdominal pain+1.061×syncope+0.428×lower limb pain/numbness-0.365×emergency admission-1.933×direct admission-1.493×diagnosis before referral+0.662×preoperative systolic blood pressure (SBP) < 100 mmHg (1 mmHg = 0.133 kPa)+0.632×hypersensitivity cardiac troponin I (hs-cTnI) > 34.2 ng/L+1.402×De Bakey type+0.641× pulmonary infection+1.472×postoperative delirium. The area under the ROC curve (AUC) and 95% confidence interval (95% CI) of the AAD death risk prediction model were 0.873 (0.817-0.928), and that of the verification group was 0.828 (0.740-0.916). DCA showed that the net benefit value of the model was higher. The calibration curve showed that there was a good correlation between the actual observation results and the model prediction results. Conclusion:The AAD death risk prediction model based on abdominal pain, syncope, lower limb pain/numbness, mode of admission, diagnosis before referral, preoperative SBP < 100 mmHg, hs-cTnI > 34.2 ng/L, De Bakey type , pulmonary infection, and postoperative delirium can effectively help clinicians identify patients at high risk for AAD, evaluate their postoperative survival and timely adjust treatment strategies.