OBJECTIVETo establish a method for determination of 7-ethyl-10-hydroxycamptothecin (SN-38) in microdialysates from rat brain.

METHODSThe concentrations of SN-38 were measured by LC-MS/MS method with Agilent Eclipse Plus C18 (2.1 mm ×100 mm, 1.8 μm) reversed phase column using acetonitrile-0.1% methanoic acid as mobile phase with gradient elution at a flow rate of 0.3 ml/min and temperature at 35 degree. Multiple reaction monitoring using the precursor to product ion combinations of m/z 393.1→349.1 was performed to detect SN-38 in microdialysates from rat brain.

RESULTSBlank microdialysate had non-interference. The method was linear over the concentration range of 0.1015-1015 ng/ml (r=0.9995); and the lower limit of quantification (LOQ) was 0.1015 ng/ml. The recovery of assay for SN-38 ranged from 97.54%-100.60%. The intra- and inter-day precision and stability were both well. The concentrations of SN-38 in brain microdialysates presented pharmacokinetics process and achieved the peak after 220 min.

CONCLUSIONThe fully validated LC-MS/MS analytical method has high specificity and sensibility, which can be used effectively to analyze SN-38 in microdialysates from rat brain.

Animals ; Brain Chemistry ; Camptothecin ; analogs & derivatives ; analysis ; Chromatography, Liquid ; methods ; Male ; Microdialysis ; Rats ; Rats, Sprague-Dawley ; Sensitivity and Specificity ; Tandem Mass Spectrometry ; methods

Objective To explore the mechanisms of ligament of Marshall (LOM) initiat and sustain atrial fibrillation (AF).Methods The electrophysiologic properties of canine LOM were investigated using multipolar catheter mapping(normal canines,n =4,group A;AF canines,n =5,group B).The programmed stimulation were performed in the LOM,PV-left atrium(LA)junction and LA,respectively.Activations maps of LOM were analyzed from episodes of spontaneous onset of AF and initiation of induced AF by a single extrastimulus.The effectives refractory period of each part was compared and statistically analyzed among three parts in each group and between the two groups.LOM were cutted with surgical incision technology.The inducing rate of AF and the mapping rate of double potential and fragmented electrocardiogram were compared and statistically analyzed pro and post isolation of LOM.Results The incidence of abnormal potential of LOM in the two groups was significantly different(P ＜0.01),re-entry cycle(group A 25％ vs.B group 80％),tachycardia(group A 25％ vs.B 100％),double potential(group A 25％ vs.group B 80％),fragmentation potential(group A 25％ vs.group 80％).There was a significant difference in the rate of LOM tachycardia induction before and after LOM intervention in group B (P ＜ 0.05,before 100％ vs.after 20％).Conclusion There are two possible mechanisms of LOM involved in the occurrence and maintenance of AF:one is that LOM induces AF through spontaneous excitation,the other is that LOM participates in the reentry of left atrium and pulmonary vein in the form of bypass to induce and maintain AF.

Objective:To analyze the role of baseline mesorectal fascia (MRF) status and the correlation between MRF changes and prognosis after neoadjuvant therapy in patients with locally advanced rectal cancer.Methods:Totally 321 patients with locally advanced rectal cancer were retrospectively analyzed from January 2014 to December 2016 in Peking University Cancer Hospital. All patients underwent surgery after neoadjuvant radiotherapy and chemotherapy, and were followed up regularly after surgery. The MRF status, extramural vascular invasion (EMVI) status, tumor location, tumor stage and lymph node status were evaluated on baseline MRI. For patients with positive baseline MRF, preoperative MRF status was also evaluated. Chi-square test or independent t test were used to compare the characteristics between MRF positive and negative patients. Kaplan-Meier curve, log-rank test and multivariate Cox regression were used to analyze the correlation between imaging features and prognosis. Results:In all of the 321 subjects, 193 (60.1%) had positive baseline MRF, 54 (28.0%) of the 193 patiens had negative MRF after neoadjuvant therapy, and 139 (72.0%) of them still had positive MRF preoperatively. The postoperative pathological T and N stages were significantly higher in patients with positive baseline MRF than those with negative MRF, and the proportion of patients achieving complete pathological response was significantly lower than those with negative MRF (all P<0.05). The postoperative pathological T and N stages of patients with MRF negative conversion were significantly lower than those without MRF negative conversion. In patients with negative baseline MRF and patients with negative MRF conversion after neoadjuvant therapy, the proportion of positive MRI EMVI was significantly lower (all P<0.05). Univariate survival analysis showed that overall survival and metastasis free survival were poorer in patients with positive MRF at baseline, with a hazard ratio of 3.33 and 1.69, respectively. There was no significant correlation between negative MRF conversion after neoadjuvant therapy and overall survival, metastasis free survival and recurrence free survival. Multivariate Cox analysis showed that baseline MRF and EMVI status were independent factors for overall survival and metastasis free survival, with a risk ratio of 2.15 and 3.35 for overall survival, 1.13 and 2.74 for metastasis free survival, respectively. Conclusions:Baseline MRF status is one of the independent prognostic predictors in locally advanced rectal cancer patients with neoadjuvant therapy. However, the role of the change in MRF status after neoadjuvant therapy is uncertain for predicting prognosis.