[Research progress of traditional Chinese medicine intervention for ulcerative colitis based on Notch1 signaling pathway].

Ulcerative colitis(UC) is one of the common gastrointestinal diseases worldwide. In recent years, the incidence of UC has been continuously increasing, seriously threatening the health of people globally. It thus has become an urgent problem that needs to be addressed. There is research evidence that intestinal mucosal barrier dysfunction, including changes in intestinal stem cell secretion lineage, mucosal layer damage, disruption of cell junctions, overactive immune function, and imbalanced gut microbiota, is an important pathogenic factor and molecular basis of UC. The Notch signaling pathway is a highly conserved signaling pathway in eukaryotes during evolution, which transmits signals through cell connections between adjacent cells, affecting a series of processes such as cell proliferation, differentiation, development, migration, and apoptosis. Therefore, the Notch signaling pathway can regulate intestinal stem cells, CD4~+T cells, innate lymphoid cells(ILCs), macrophages(MØ), and intestinal microbiota and thus affect the chemical, physical, immune, and biological mucosal barriers of the intestinal mucosa. Its function is extensive and unique, different from those signaling pathways that mainly focus on anti-inflammatory and antioxidant stress. It can explain the therapeutic effects of traditional Chinese medicine from different perspectives. This article reviewed the role of the Notch1 signaling pathway in the pathogenesis of UC and the relevant literature on the targeted prevention and treatment of UC with traditional Chinese medicine, so as to provide new targets and theoretical support for further research on the effective prevention and treatment of UC.

Initial experience of visualized biliary cannulation during ERCP.

BACKGROUND : Selective biliary cannulation is the most challenging step in endoscopic retrograde cholangiopancreatography (ERCP) because only indirect radiographic images can be obtained. Therefore, we developed a novel endoscopic retrograde direct cholangioscopy (ERDC) technology to facilitate visible biliary cannulation. METHODS : In this case series, we used ERDC to treat 21 patients with common bile duct stones who were enrolled consecutively between July 2022 and December 2022. The procedure details and complications were recorded, and all patients were followed up for 3 months after the procedure. The learning curve effect was analyzed by comparing the early and later cases. RESULTS : Biliary cannulation was successful in all patients, and the stones were removed completely. The median (interquartile range [IQR]) time for cholangioscopy-guided biliary cannulation was 240.0 (10.0-430.0) seconds, and the median (IQR) number of cannulation procedures was 2 (1-5). Despite there being one episode of post-ERCP pancreatitis, one of cholangitis, and three patients developing asymptomatic hyperamylasemia, all of the patients recovered after symptomatic treatment, being discharged and with no serious adverse events occurring during the 3-month follow-up period. Compared with the early cases, the number of intubations and the use of guidewire guidance decreased in later cases. CONCLUSION : Our research confirms that ERDC is a feasible technology for biliary cannulation under direct vision.

A clinically feasible circulating tumor cell sorting system for monitoring the progression of advanced hepatocellular carcinoma.

BACKGROUND: Hematogenous metastasis is essential for the progression of advanced hepatocellular carcinoma (HCC) and can occur even after patients receive multidisciplinary therapies, including immunotherapy and hepatectomy; circulating tumor cells (CTCs) are one of the dominant components of the metastatic cascade. However, the CTC capture efficiency for HCC is low due to the low sensitivity of the detection method. In this study, epithelial cell adhesion molecule (EpCAM)/vimentin/Glypican-3 (GPC3) antibody-modified lipid magnetic spheres (LMS) were used to capture tumor cells with epithelial phenotype, mesenchymal phenotype and GPC3 phenotype, respectively, in order to capture more CTCs with a more comprehensive phenotype for monitoring tumor metastasis. RESULTS: The novel CTC detection system of Ep-LMS/Vi-LMS/GPC3-LMS was characterized by low toxicity, strong specificity (96.94%), high sensitivity (98.12%) and high capture efficiency (98.64%) in vitro. A sudden increase in CTC counts accompanied by the occurrence of lung metastasis was found in vivo, which was further validated by a clinical study. During follow-up, the rapid increase in CTCs predicted tumor progression in HCC patients. Additionally, genetic testing results showed common genetic alterations in primary tumors, CTCs and metastatic tissues. The proportion of patients predicted to benefit from immunotherapy with the CTC detection method was higher than that for the tissue detection method (76.47% vs. 41.18%, P = 0.037), guiding the application of clinical individualized therapy. CONCLUSIONS: The Ep-LMS/Vi-LMS/GPC3-LMS sequential CTC capture system is convenient and feasible for the clinical prediction of HCC progression. CTCs captured by this system could be used as a suitable alternative to HCC tissue detection in guiding immunotherapy, supporting the clinical application of CTC liquid biopsy.

Systematic analysis of gene expression profiles reveals prognostic stratification and underlying mechanisms for muscle-invasive bladder cancer.

BACKGROUND: Muscle-invasive bladder cancer (MIBC) is originated in the muscle wall of the bladder, and is the ninth most common malignancy worldwide. However, there are no reliable, accurate and robust gene signatures for MIBC prognosis prediction, which is of the importance in assisting oncologists to make a more accurate evaluation in clinical practice. METHODS: This study used univariable and multivariable Cox regression models to select gene signatures and build risk prediction model, respectively. The t-test and fold change methods were used to perform the differential expression analysis. The hypergeometric test was used to test the enrichment of the differentially expressed genes in GO terms or KEGG pathways. RESULTS: In the present study, we identified three prognostic genes, KLK6, TNS1, and TRIM56, as the best subset of genes for muscle-invasive bladder cancer (MIBC) risk prediction. The validation of this stratification method on two datasets demonstrated that the stratified patients exhibited significant difference in overall survival, and our stratification was superior to three other stratifications. Consistently, the high-risk group exhibited worse prognosis than low-risk group in samples with and without lymph node metastasis, distant metastasis, and radiation treatment. Moreover, the upregulated genes in high-risk MIBC were significantly enriched in several cancer-related pathways. Notably, PDGFRB, a receptor for platelet-derived growth factor of PI3K-Akt signaling pathway, and TUBA1A were identified as two targets of multiple drugs. In addition, the angiogenesis-related genes, as well as two marker genes of M2 macrophage, CD163 and MRC1, were highly upregulated in high-risk MIBC. CONCLUSIONS: In summary, this study investigated the underlying molecular mechanism and potential therapeutic targets associated with worse prognosis of high-risk MIBC, which could improve our understanding of progression of MIBC and provide new therapeutic strategies for the MIBC patients.

Identification of discrepancy between CTLA4 expression and CTLA4 activation in gastric cancer.

Objective: Recently, immune checkpoints blockers showed higher anti-tumor activity for advanced gastric cancer (GC). The purpose of the study is to find out predictive biomarkers related to anti-cytotoxic lymphocyte antigen 4 (CTLA4) therapy. Materials and methods: Datasets of gene expression omnibus (GEO), the cancer genome atlas (TCGA), and gene set enrichment analysis (GESA) were extracted. Differential expression of CTLA4 between cancer tissues and normal mucosa, enrichment of WT (wild type) vs. CTLA4_KO (knockout) upregulated gene set and clinical significance were analyzed. The expression of CTLA4, CD3, and granzyme A (GZMA) were validated on 30 cases of Chinese GC. Microsatellite instability (MSI) marker MLH1 and Epstein-Barr virus (EBV) marker EBER were examined on 30 cases of Chinese GC by immunohistochemistry and in situ hybridization. Results: CTLA4 was upregulated in GC tissue relative to normal mucosa in datasets of GSE27342 (fold change = 1.586, p < .001) and GSE63089 (fold change = 1.365, p < .001). Increased CTLA4 expression was positively related to CTLA4 activation. EBV-associated GC (EBVaGC) and microsatellite instability GC (MSIGC) disclosed higher CTLA4 levels than other GCs. Genomic stability GC (GSGC) also showed higher enrichment score of CTLA4 activation. CTLA4 activation resulted in shorter overall survival in GC. The expression level of CTLA4 was well correlated to expression levels of GZMA (R = 0.701, p < .001) and CD3 (R = 0.750, p < .001). Conclusions: Based on bioinformatics analysis, GSGC should be worth noticed as a potential GC subtypes responsive to anti-CTLA4 treatment.

Factors associated with mortality risk for malignant colonic obstruction in elderly patients.

BACKGROUND: Acute colonic obstruction is the most common complication of colorectal cancer (CRC) in elderly patients. Medical treatment has been associated with higher perioperative morbidity and mortality rates. There is a need for identification of elderly CRC patients who will do poorly so that results can be improved. The purpose of this study is to assess the 30-day outcome of elderly patients undergoing malignant colonic obstruction procedures and identify the associated factors of mortality. METHODS: A review of 233 elderly patients who received medical procedures for malignant colonic obstruction between April 2000 and April 2012 was conducted. Data regarding clinical variables, surgical procedures and outcomes, complications, and mortality were studied. Univariate and logistic regression analyses were performed on mortality risk factors. RESULTS: Patients had a mean age of 78.2 years (range 70-95). A total of 126 (54.1%) patients were classified ASA III and above. Eighty (34.3%) patients had right-sided colonic obstruction. In the 153 (65.7%) patients with left-sided colonic obstruction, 40 patients received self-expandable metallic stent (SEMS) treatment and 193 patients received surgery. A total of 62.2% (n = 145) patients had post operation complications. The overall 30-day mortality was 24.5% (n = 57). ASA grading, peritonitis and Dukes staging were independent risk factors for mortality. CONCLUSIONS: Medical procedures in elderly patients with malignant colonic obstruction are associated with significant complications and mortality. Identifying these high-risk patients and treating promptly may improve outcomes. SEMS treatment provides a useful alternative to surgical intervention.

Ultrasensitive enantiomeric barbiturate analysis in body fluids through capillary electrophoresis with large volume sample stacking and ultrasound assisted dispersive liquid liquid microextraction.

A rapid, straightforward, and sensitive approach to quantifying enantiomeric barbiturates in serum was developed by integrating ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) with large-volume sample stacking (LVSS) in capillary electrophoresis (CE). UA-DLLME was employed for sample preparation, and on-column preconcentration by using LVSS with polarity switching was implemented to enhance sensitivity. We thoroughly investigated and optimized various parameters influencing extraction and stacking to achieve optimal detection performance with the highest enrichment efficiencies. Under optimal extraction conditions (injection of a mixed solution containing 40 µL of CHCl3 and 200 µL of tetrahydrofuran into 1 mL of a sample solution at pH 10.0), LVSS was performed using 600 mM Tris-boric acid (pH 9.5) containing 35 mM hydroxypropyl-ß-cyclodextrin and sodium taurodeoxycholate hydrate. A voltage of 20 kV was applied and a preinjection water plug was loaded at a height of 25 cm for 10 s. Subsequently, the sample solution was injected at a height of 25 cm for 480 s, after which a voltage of -20 kV was applied and the sample stacking was initiated. The stacking process was completed when 95 % of the separation current was attained. Under optimized conditions, the contraction folds of the four barbiturate analytes (R, S-Secobarbital, R, S-pentobarbital) were improved by approximately 6400-fold, achieving detection limits of 0.1 ng/mL. The limits of quantification for all analyte enantiomers were 0.5-50 ng/mL, demonstrating good linearity (r > 0.997). Migration times exhibited a relative standard deviation of less than 1.7 %, whereas peak areas for the four analytes exhibited a deviation of 8.7 %. Finally, the established method was effectively applied to the analysis of human serum samples.

P3MOT-decorated metal-porphyrin-based zirconium-MOF for the efficient electrochemical detection of 4-nitrobenzaldehyde.

A novel hybrid composite integrating conductive poly-3-methoxythiophene and PCN-222(Fe) (porphyrin-metal-organic frameworks) was synthesized using an in situ polymerization strategy. Leveraging the large specific area of MOFs and the low electrical resistance of conductive polymers, the modified electrode proved to be a promising candidate for the electrochemical detection of 4-nitrobenzaldehyde. The electrocatalytic response was measured using differential pulse voltammetry techniques and cyclic voltammetry, where the linear concentration range of analyte detection was estimated to be 0-900 µM and the detection limit was 0.233 µM with high selectivity toward the analyte. The sensor demonstrated repeatability and stability, allowing the direct electroanalytical measurement of 4-nitrobenzaldehyde in real samples with reliable recovery. This methodology expands the application of porphyrin MOFs for the electroanalytical sensing of environmental contaminants.

Compressibility of lime-treated dredged slurry with high water content.

Lime is widely used for soft ground treatment, rendering the compressibility of lime-treated soil a crucial factor in deformation analysis in engineering applications. This study investigated the compressibility of three remoulded lime-treated slurries with high water content in Southeast China. Sixty groups of oedometer tests were conducted on lime-treated soils with an initial water content of 1 to 3 times the liquid limit and lime contents between 1 and 3%. The oedometer test results were discussed to examine the remoulded yield stress σ y ' of lime-treated slurry. Considering the relationships between σ y ' , the void ratio, lime content, and initial water content were preliminarily discussed and quantitatively established. Research on the normalised compression curve of lime-treated soil revealed that for soil samples containing a lime content of 0-%, the normalised compression curve at σ p ' > σ y ' can be represented by a unique line. Furthermore, the log(1 + e) - log σ v ' compression curve of lime-treated slurry at pre-yield state is analysed, and a prediction method for the modified compression index is proposed.

Maillard Reaction Inspired Microexplosion toward Fast Synthesis of Two-Dimensional Mesoporous Tin Oxides for Efficient Chemiresistive Gas Sensing.

Two-dimensional (2D) mesoporous transition metal oxides are highly desired in various applications, but their fast and low-cost synthesis remains a great challenge. Herein, a Maillard reaction inspired microexplosion approach is applied to rapidly synthesize ultrathin 2D mesoporous tin oxide (mSnO2). During the microexplosion between granular ammonia nitrate with melanoidin at high temperature, the organic species can be carbonized and expanded rapidly due to the instantaneous release of gases, thus producing ultrathin carbonaceous templates with rich functional groups to effectively anchor SnO2 nanoparticles on the surface. The subsequent removal of carbonaceous templates via calcination in air results in the formation of 2D mSnO2 due to the confinement effect of the templates. Pd nanoparticles are controllably deposited on the surface of 2D mSnO2 via in situ reduction, forming ultrathin 2D Pd/mSnO2 nanocomposites with thicknesses of 6-8 nm. Owing to the unique 2D mesoporous structure with rich oxygen defects and highly exposed metal-metal oxide interfaces, 2D Pd/mSnO2 exhibits excellent sensing performance toward acetone with high sensitivity, a short response time, and good selectivity under low working temperature (100 °C). This fast and convenient microexplosion synthesis strategy opens up the possibility of constructing 2D porous functional materials for various applications including high-performance gas sensors.

Different expression of S100A8 in malignant and benign gallbladder diseases.

BACKGROUND: Proteomic analysis is a powerful tool for complete establishment of protein expression. Comparative proteomic analysis of human bile from malignant and benign gallbladder diseases may be helpful in research into gallbladder cancer. AIMS: Our objective was to establish biliary protein content for gallbladder cancer, gallbladder adenoma, and chronic calculous cholecystitis for comparative proteomic analysis. METHODS: Bile samples were collected from patients with gallbladder cancer, gallbladder adenoma, and chronic calculous cholecystitis. Peptides of biliary proteins were separated by two-dimensional liquid chromatography then identified by tandem mass spectrometry. RESULTS: Up to 544, 221, and 495 unique proteins were identified in bile samples from gallbladder cancer, gallbladder adenoma, and chronic calculous cholecystitis. Forty-three, 16, and 28 proteins with more than one unique peptide, respectively, were identified in the three groups. Among these, 30 proteins including S100A8 were overexpressed in gallbladder cancer, compared with benign gallbladder diseases. We also confirmed, by immunohistochemical analysis, that S100A8 is more abundant in tumor-infiltrating immune cells in cancerous tissue. CONCLUSIONS: Compared with benign gallbladder diseases, consistently elevated S100A8 levels in malignant gallbladder bile and tissue indicate that gallbladder cancer is an inflammation-associated cancer. S100A8 may be a biomarker for gallbladder cancer.

[Establishment of a high metastatic potential human hepatocellular carcinoma orthotopic transplantation model with palliative liver resection in nude mice].

OBJECTIVE: To construct a high metastatic potential human hepatocellular carcinoma (HCC) orthotopic transplantation model with palliative liver resection in nude mice. METHODS: A human HCC orthotopic nude mice model was established by administering a single inoculation of the highly metastatic MHCC97H tumor tissue (size 2 mm * 2 mm * 2 mm) into the left liver lobe. At day 14 post-inoculation, a random group of the mice received palliative liver resection; the unresected mice served as controls. Changes in expression levels of 113 genes with metastasis-related functions were evaluated in the residual HCC tissues. At day 35 post-resection, a random group of the mice were sacrificed by cervical dislocation and a comprehensive metastases examination was performed. The remaining mice were used to observe life span. All statistical analyses were performed by the SPSS v17.0 software, and significance was defined as P less than 0.05. RESULTS: The nude mouse model of highly metastatic HCC with palliative liver resection was successfully established. Incidences of intrahepatic and abdominal metastases were higher in the palliative resected group (vs. unresected group: 11.7+/-4.7 vs. 6.3+/-2.8, t = -2.412, P less than 0.05 and 9.8+/-3.4 vs. 5.2+/-2.6, t = -2.641, P less than 0.05 respectively). In addition, the palliative resected group showed significantly enhanced pulmonary metastasis (vs. unresected group: 14.3+/-4.7 vs. 8.7+/-4.7, t = -2.348, P less than 0.05). Differential gene expression levels were found for MTSS1, TGFbl, SMAD2, IL-1b, and MMP7, and were situated in the central position of gene function net of residual HCC. The life-span of the palliative resected group was significantly longer than that of the unresected group (60.8+/-2.7 vs. 51.3+/-1.4 days, x2 = 12.850, P less than 0.01). CONCLUSION: The highly metastatic human HCC nude mouse model with palliative liver resection that was successfully constructed in this study represents a useful investigational tool to assess the biological characteristics of residual cancer and to screen therapeutic strategies.

Metal-organic framework-derived trimetallic oxides with dual sensing functions for ethanol.

Metal-organic framework (MOF)-derived metal oxide semiconductors have recently received extensive attention in gas sensing applications due to their high porosity and three-dimensional architecture. Still, challenges remain for MOF-derived materials, including low-cost and facile synthetic methods, rational nanostructure design, and superior gas-sensing performances. Herein, a series of Fe-MIL-88B-derived trimetallic FeCoNi oxides (FCN-MOS) with a mesoporous structure were synthesized by a one-step hydrothermal reaction followed by calcination. The FCN-MOS system consists of three main phases: α-Fe2O3 (n-type), CoFe2O4, and NiFe2O4 (p-type), and the nanostructure and pore size can be controlled by altering the content of α-Fe2O3, CoFe2O4, and NiFe2O4. The sensors based on FCN-MOS exhibit a high response of 71.9, a good selectivity towards 100 ppm ethanol at 250 °C, and long-term stability up to 60 days. Additionally, the FCN-MOS-based sensors show a p-n transition gas sensing behavior with the alteration of the Fe/Co/Ni ratio.

Potential contribution of the gut microbiota to the development of portal vein thrombosis in liver cirrhosis.

Background: Portal vein thrombosis (PVT) is a serious complication of liver cirrhosis (LC) and is closely related to gut homeostasis. The study aimed to investigate the composition of gut microbiota and its putative role in PVT development in LC. Methods: 33 patients with LC admitted between January 2022 and December 2022 were enrolled in this study. Based on imaging findings, they were categorized into LC without PVT (n = 21) and LC with PVT (n = 12) groups. Fecal samples were collected from each participant and underwent 16S rDNA sequencing. Results: D-Dimer and platelet elevations were the main clinical features of LC with PVT. The alpha and beta diversity of the gut microbiota in LC with PVT group was found to be significantly higher compared to the control group. The structure of the gut microbiota was significantly different between the two groups. Based on LEfSe data, the genera Akkermansia, Eubacterium hallii group, Fusicatenibacter, and Anaerostipes were enriched in the LC with PVT, while Enterococcus, Weissella, Bacteroides, and Subdoligranulum were enriched in those of the LC subjects. Changes in microbiota structure result in significant differences in gut microbiota metabolism between the two groups. Altered levels of the microbiota genera were shown to be correlated with coagulation factor parameters. In animal experiments, the addition of Bacteroides reversed the CCl4-induced PVT. Conclusion: Liver cirrhosis with PVT led to a disorder in the gut microbiota, which was characterized by an increase in pathogenic bacteria and a decrease in beneficial bacteria. Furthermore, modulating the gut microbiota, especially Bacteroides, may be a promising therapeutic approach to reduce the progression of PVT in LC.

Solvent-pair surfactants enabled assembly of clusters and copolymers towards programmed mesoporous metal oxides.

Organic-inorganic molecular assembly has led to numerous nano/mesostructured materials with fantastic properties, but it is dependent on and limited to the direct interaction between host organic structure-directing molecules and guest inorganic species. Here, we report a "solvent-pair surfactants" enabled assembly (SPEA) method to achieve a general synthesis of mesostructured materials requiring no direct host-guest interaction. Taking the synthesis of mesoporous metal oxides as an example, the dimethylformamide/water solvent pairs behave as surfactants and induce the formation of mesostructured polyoxometalates/copolymers nanocomposites, which can be converted into metal oxides. This SPEA method enables the synthesis of functional ordered mesoporous metal oxides with different pore sizes, structures, compositions and tailored pore-wall microenvironments that are difficult to access via conventional direct organic-inorganic assembly. Typically, nitrogen-doped mesoporous ε-WO3 with high specific surface area, uniform mesopores and stable framework is obtained and exhibits great application potentials such as gas sensing.

Exosomal proteomics identifies RAB13 as a potential regulator of metastasis for HCC.

BACKGROUND: Exosomal proteins from cancer cells are becoming new biomarkers for cancer monitoring and efficacy evaluation. However, their biological function and molecular mechanism underlying tumor metastasis are largely unknown. METHODS: Bioinformatic methods such as bulk gene expression analysis, single-cell RNA sequencing data analysis, and gene set enrichment analysis were employed to identify metastasis-associated proteins. The in vitro and in vivo experiments were used to investigate the function of RAB13 in HCC metastasis. RESULTS: We identified RAB13 as one of the critical regulators of metastasis in HCC-derived exosomes for the first time. In vitro, the invasiveness of HCC cell lines could be attenuated by RAB13 silence. In vivo, tumor size and proportion of high-grade lung metastatic nodule could be reduced in the mice with orthotopic transplantation of tumors and intravenously injected with exosomes derived from MHCC97H cell with RAB13 silence (si-RAB13-Exo), as compared with those without RAB13 silence (si-NC-Exo). Moreover, in si-RAB13-Exo group, circulating tumor cell counts were decreased at the third, fourth, and fifth weeks after orthotopic transplantation of tumors, and MMP2 (matrix metalloproteinase 2)/TIMP2 (tissue inhibitor of metalloproteinases 2) ratio was also significantly decreased. In addition, RAB13 expression was also associated with VEGF levels, microvessel density, and tube formation of vascular endothelial cells by both in vitro and in vivo models, indicating that RAB13 was associated with angiogenesis in HCC. CONCLUSIONS: We have demonstrated exosomal RAB13 as a potential regulator of metastasis for HCC by in silico, in vitro, and in vivo methods, which greatly improve our understanding of the functional impact of exosomal proteins on HCC metastasis.

Decreasing pancreatic leak after distal pancreatectomy: bovine pericardium wrapping stump in a porcine model.

BACKGROUND: Despite marked improvements in pancreatic surgery, the high incidence and morbidity of pancreatic leak after resection has remained unchanged. The current study investigated the safety and efficacy of bovine pericardium wrapping stump after distal pancreatectomy in a porcine model. METHODS: Thirty-two swine were randomly assigned to control and experiment groups to undergo conventional scalpel transection with single hand-sewn closure of the pancreatic remnant (control) or bovine pericardium wrapping stump combined with hand-sewn closure (experiment). Closed-suction drainage was collected and measured daily. Animals were necropsied at 3 weeks postoperatively, and the pancreatic remnants were examined for histology. Primary end points were the development of a pancreatic fistula defined as greater than threefold drain/serum amylase after the 3rd postoperative day, and the presence of undrained amylase-rich fluid collections/abscess. RESULTS: The incidence of pancreatic leak in the wrapping group was 6.3 versus 46.7% in the control group (p < 0.05). The amount of drainage fluid was higher in the control group than the experiment group during the postoperative days. There were no differences in operative time or other clinical parameters measured. No other significant differences were found in macroscopic changes between groups at reexploration. Histological examination demonstrated focal, chronic inflammation with necrosis in all animals. CONCLUSIONS: Bovine pericardium wrapping stump effectively reduced the incidence of pancreatic leakage after the distal pancreatectomy.