Objective To investigate the relationship between Ct value of mice liver and postmortem interval (PMI) under various ambient temperatures. Methods mice were stored at 10℃, 15℃, 20℃, 25℃ and 30℃ after execution, and total RNA was extracted from mice liver every 6 hours (PMI 6h to 72h). The levels of 18s rRNA were examined using real-time PCR. The results were expressed by cycle threshold (Ct) value to explore relationship between PMI and Ct value, and the interpolation functions were established to estimate PMI. Results In each group, Ct value increased with PMI increased. Surface equation was obtained after interpolation analysis on temperature range 10℃~30℃. The three-variable quintic surface equation was f(x, y)=-426.9+30.82x+44.48y-1.297x2-1.837xy-1.388y2+0.034 38x3+0.038 17x2y+0.038 67xy2+0.028 77y3-0.000 612 9x4-3.897e-7x3y-0.001 223x2y2+0.000 256 6xy3-0.000 537 4y4+3.606e-6x5-2.846e-6x4y+1.009e-5x3y2-3.439e-6x2y3-2.556e-7xy4+2.664e-6y5(r2=0.999 4). Conclusion The rule of Ct value changes at ambient temperature complied with three-variable quintic surface equation distribution. Measurement of interpolation function may be used for PMI estimation at ambient temperature.

Objective:To explore the value of tacrolimus blood concentration and other related indexes in evaluating early postoperative infection in patients with liver transplantation.Methods:Patients with complete medical records who underwent liver transplantation in the First Affiliated Hospital of Nanjing Medical University from January 2014 to December 2019 were screened. Cohort study was used, and demographic data, laboratory test results, tacrolimus blood concentration and other data of patients with liver transplantation were collected. All patients with postoperative infection were divided into four groups, inculding two to four weeks, five to 12 weeks, 13 to 52 weeks and >52 weeks groups, and uninfected patients in each group were matched 1∶1 according to age ± 3 years old. Independent sample t test and rank sum test were used to analyze the differences in clinical data between postoperative infected and uninfected patients with liver transplantation patients. Logistic regression analysis was used to explore the influencing factors of infection in the early postoperative period (two to four weeks after operation). The relative safe value of tacrolimus blood concentration in the early postoperative period was evaluated by receiver operating characteristic curve. Results:A total of 150 patients with infection after liver transplantation were included, including 65 patients in the two to four weeks group, 31 patients in the five to 12 weeks group, 27 patients in the 13 to 52 weeks group, and 27 patients in the >52 weeks group. There were 52, 30, 32, and 39 uninfected patients in the four groups, respectively. There were 247 males (81.52%) in 303 patients with liver transplantation, and the age ranged from 10 to 78 years old. Hepatitis B cirrhosis and hepatocellular carcinoma were the main primary diseases, accounting for 41.91%(127/303) and 47.52%(144/303), respectively. The tacrolimus blood concentration and alanine aminotransferase in patients with infection in the two to four weeks group were (11.46±4.94) μg/L and 118.20(38.80, 215.80) U/L, respectively, which were both higher than those in the uninfected group ((7.12±2.33) μg/L and 39.40(23.40, 142.70) U/L, respectively). The differences were both statistically significant ( t=6.26, Z=2.66, respectively, both P<0.05). Sputum sources accounted for the largest number of samples, accounting for 61.6%(98/159). A total of 174 pathogens were isolated, of which gram-negative bacteria (55.2%(96/174)) were the majority, mainly Klebsiella pneumoniae (20.1%(35/174)) and Acinetobacter baumannii (13.8%(24/174)). Multivariate analysis showed that tacrolimus blood concentration (odds ratio ( OR)=1.634, 95% confidence interval ( CI) 1.298 to 2.058, P=0.001) was a risk factor for infection at two to four weeks after liver transplantation, while lymphocyte count ( OR=0.165, 95% CI 0.057 to 0.474, P=0.010) was a protective factor. The area under the curve of tacrolimus blood concentration in evaluating the infection at two to four weeks after liver transplantation was 0.817. The cut-off value was 8.7 μg /L ( P<0.05), with the sensitivity of 0.708 and the specificity of 0.846. Conclusions:The main site of infection in patients with liver transplantation is respiratory system. Gram-negative bacilli are the main pathogens. When tacrolimus blood concentration is below 8.7 μg/L at two to four weeks after liver transplantation, the probability of infection in the early postoperative period may be reduced.