Porcine reproductive and respiratory syndrome virus(PRRSV)mainly causes sow abor-tion,stillbirth,mummified fetus and respiratory symptoms in piglets.Since first reported in China in 1996,the virus complexity has increased significantly in more than 20 years of genetic evolution,bringing huge economic losses to the pig industry.In recent years,with the emergence of various PRRSV recombinant virus strains,preventing and controlling this epidemic became increasingly difficult.The purpose of this article is to comprehensively review the genome structure and func-tion of PRRSV,RNA virus recombination mechanism,main types of recombination,and the epi-demic status and recombination for the dominant epidemic PRRSV strains,in order to provide clues for in-depth research on gene recombination of PRRSV,thus providing the theoretical sup-port for formulating scientific prevention and control strategies.

Objective:To determine the actual metastasis rate of paracolic lymph nodes (PCN) more than 10 cm proximal to rectal tumors and explore the significance of PCN dissection in the prognosis of patients with rectal cancer. ?Methods:This was a prospective observational cohort study. The clinical data of 457 consecutive patients with rectal cancer who underwent radical surgery at the Colorectal Tumor Center of West China Hospital, Sichuan University from January 2015 to May 2022 were included. Inclusion criteria: (1) Pathologically confirmed rectal adenocarcinoma (anal margin ≤ 12 cm); (2) R0 resection was performed with a proximal margin ≥ 10 cm (measured on the in vivo specimen during surgery after intestinal mobilization); (3) For stage IV patients, only those with resectable metastatic lesions by R0 were included; (4) Patients who completed the full course of neoadjuvant therapy (TNT) must meet the surgical window of 8-12 weeks after radiotherapy. Exclusion criteria: tumors located more than 15 cm from the anal margin, synchronous multiple primary colorectal cancers, positive tumor margins, preoperative imaging suggesting lateral lymph node metastasis (LLNM), presence of Lynch syndrome or familial adenomatous polyposis, emergency surgery, recurrence after rectal cancer surgery, T4b tumors requiring combined organ resection, previous radiotherapy and chemotherapy for non-rectal cancer, and those with cardiac, pulmonary, renal and other organ dysfunction that could not tolerate surgery. After standard total mesorectal excision (TME), the proximal intestinal tube was transected at a level more than 10 cm above the lesion, and then intestinal anastomosis or enterostomy was completed. The distance from the tumor edge was marked and measured in vivo during the operation, and lymph nodes were harvested from the fresh specimen. Patients with PCN metastasis beyond 10 cm proximal to the tumor were classified into the positive lymph node group (pPCN group), while those without PCN metastasis beyond 10 cm proximal to the tumor were classified into the negative lymph node group (nPCN group). The differences in clinicopathological characteristics, overall survival (OS) and disease-free survival (DFS) between the two groups were compared, and risk factor analysis and survival analysis of pPCN were performed.Results:There were 16 cases (3.5%) in the pPCN group, 15 cases (3.3%) had central lymph node metastasis; the nPCN group included 441 cases. When comparing the baseline characteristics between the pPCN group and the nPCN group, there was no statistically significant difference in other aspects except that the cN stage was more advanced in the pPCN group ( P=0.006) (all P>0.05). The number of positive mesenteric lymph nodes in the pPCN group was higher than that in the nPCN group ( P<0.001), and the proportion of patients with a total number of harvested lymph nodes ≥12 and the number of lymph nodes with a short diameter >5 mm were both higher (all P<0.05). The proportion of patients with positive lymph nodes within 10 cm and the number of positive lymph nodes within 10 cm were also higher in the pPCN group (both P<0.001). Similar to the clinical TNM staging, the proportions of patients with pT3 and N2 stages, as well as the incidence of poorly differentiated tumors (G3, G4) were higher in the pPCN group ( P<0.001). The results of multivariate analysis showed that among the preoperative pathological characteristic variables, the presence of positive lymph nodes within 10 cm (OR=14.869, 95%CI: 2.993-73.858, P=0.001) and low tumor differentiation grade (OR=7.189, 95%CI: 2.091- 24.714, P=0.002) were independent risk factors for pPCN. The median follow-up time of the patients in this group was 63 (0-63) months. No local recurrence occurred in the pPCN group, and the 5-year OS was 50.0%, which was significantly lower than 78.0% in the nPCN group (HR=2.496, 95%CI: 1.263-4.930, P=0.008). The 3-year DFS was 43.8%, also significantly lower than 77.7% in the nPCN group (HR=2.950, 95%CI:1.488-5.846, P=0.002). Multivariate Cox prognostic analysis suggested that age ≥65 years (HR=2.041, 95%CI: 1.375-3.031, P<0.001), female (HR=1.838, 95%CI: 1.171-2.884, P=0.008), tumor length ≥3 cm (HR=1.747, 95%CI: 1.076-2.834, P=0.024), more advanced cT stage (HR=2.865, 95%CI: 1.234-6.653, P=0.014), and cM1 (HR=4.368, 95%CI: 2.480-7.694, P<0.001) were independent risk factors affecting OS. No neoadjuvant therapy (HR=0.636, 95%CI: 0.413-0.980, P=0.040) and cM1 (HR=5.556, 95%CI: 3.335-9.256, P<0.001) were independent risk factors affecting DFS. pPCN showed a tendency to be an independent risk factor for DFS (HR=1.942, 95%CI: 0.966-3.906, P=0.063). Conclusion:The incidence of pPCN is higher than expected, and the prognosis of patients is poor. Patients with high-risk factors may benefit from extended proximal intestinal resection (>10 cm) to avoid residual positive PCN, thereby reducing local recurrence.

Porcine reproductive and respiratory syndrome virus(PRRSV)mainly causes sow abor-tion,stillbirth,mummified fetus and respiratory symptoms in piglets.Since first reported in China in 1996,the virus complexity has increased significantly in more than 20 years of genetic evolution,bringing huge economic losses to the pig industry.In recent years,with the emergence of various PRRSV recombinant virus strains,preventing and controlling this epidemic became increasingly difficult.The purpose of this article is to comprehensively review the genome structure and func-tion of PRRSV,RNA virus recombination mechanism,main types of recombination,and the epi-demic status and recombination for the dominant epidemic PRRSV strains,in order to provide clues for in-depth research on gene recombination of PRRSV,thus providing the theoretical sup-port for formulating scientific prevention and control strategies.

Objective:To determine the actual metastasis rate of paracolic lymph nodes (PCN) more than 10 cm proximal to rectal tumors and explore the significance of PCN dissection in the prognosis of patients with rectal cancer. ?Methods:This was a prospective observational cohort study. The clinical data of 457 consecutive patients with rectal cancer who underwent radical surgery at the Colorectal Tumor Center of West China Hospital, Sichuan University from January 2015 to May 2022 were included. Inclusion criteria: (1) Pathologically confirmed rectal adenocarcinoma (anal margin ≤ 12 cm); (2) R0 resection was performed with a proximal margin ≥ 10 cm (measured on the in vivo specimen during surgery after intestinal mobilization); (3) For stage IV patients, only those with resectable metastatic lesions by R0 were included; (4) Patients who completed the full course of neoadjuvant therapy (TNT) must meet the surgical window of 8-12 weeks after radiotherapy. Exclusion criteria: tumors located more than 15 cm from the anal margin, synchronous multiple primary colorectal cancers, positive tumor margins, preoperative imaging suggesting lateral lymph node metastasis (LLNM), presence of Lynch syndrome or familial adenomatous polyposis, emergency surgery, recurrence after rectal cancer surgery, T4b tumors requiring combined organ resection, previous radiotherapy and chemotherapy for non-rectal cancer, and those with cardiac, pulmonary, renal and other organ dysfunction that could not tolerate surgery. After standard total mesorectal excision (TME), the proximal intestinal tube was transected at a level more than 10 cm above the lesion, and then intestinal anastomosis or enterostomy was completed. The distance from the tumor edge was marked and measured in vivo during the operation, and lymph nodes were harvested from the fresh specimen. Patients with PCN metastasis beyond 10 cm proximal to the tumor were classified into the positive lymph node group (pPCN group), while those without PCN metastasis beyond 10 cm proximal to the tumor were classified into the negative lymph node group (nPCN group). The differences in clinicopathological characteristics, overall survival (OS) and disease-free survival (DFS) between the two groups were compared, and risk factor analysis and survival analysis of pPCN were performed.Results:There were 16 cases (3.5%) in the pPCN group, 15 cases (3.3%) had central lymph node metastasis; the nPCN group included 441 cases. When comparing the baseline characteristics between the pPCN group and the nPCN group, there was no statistically significant difference in other aspects except that the cN stage was more advanced in the pPCN group ( P=0.006) (all P>0.05). The number of positive mesenteric lymph nodes in the pPCN group was higher than that in the nPCN group ( P<0.001), and the proportion of patients with a total number of harvested lymph nodes ≥12 and the number of lymph nodes with a short diameter >5 mm were both higher (all P<0.05). The proportion of patients with positive lymph nodes within 10 cm and the number of positive lymph nodes within 10 cm were also higher in the pPCN group (both P<0.001). Similar to the clinical TNM staging, the proportions of patients with pT3 and N2 stages, as well as the incidence of poorly differentiated tumors (G3, G4) were higher in the pPCN group ( P<0.001). The results of multivariate analysis showed that among the preoperative pathological characteristic variables, the presence of positive lymph nodes within 10 cm (OR=14.869, 95%CI: 2.993-73.858, P=0.001) and low tumor differentiation grade (OR=7.189, 95%CI: 2.091- 24.714, P=0.002) were independent risk factors for pPCN. The median follow-up time of the patients in this group was 63 (0-63) months. No local recurrence occurred in the pPCN group, and the 5-year OS was 50.0%, which was significantly lower than 78.0% in the nPCN group (HR=2.496, 95%CI: 1.263-4.930, P=0.008). The 3-year DFS was 43.8%, also significantly lower than 77.7% in the nPCN group (HR=2.950, 95%CI:1.488-5.846, P=0.002). Multivariate Cox prognostic analysis suggested that age ≥65 years (HR=2.041, 95%CI: 1.375-3.031, P<0.001), female (HR=1.838, 95%CI: 1.171-2.884, P=0.008), tumor length ≥3 cm (HR=1.747, 95%CI: 1.076-2.834, P=0.024), more advanced cT stage (HR=2.865, 95%CI: 1.234-6.653, P=0.014), and cM1 (HR=4.368, 95%CI: 2.480-7.694, P<0.001) were independent risk factors affecting OS. No neoadjuvant therapy (HR=0.636, 95%CI: 0.413-0.980, P=0.040) and cM1 (HR=5.556, 95%CI: 3.335-9.256, P<0.001) were independent risk factors affecting DFS. pPCN showed a tendency to be an independent risk factor for DFS (HR=1.942, 95%CI: 0.966-3.906, P=0.063). Conclusion:The incidence of pPCN is higher than expected, and the prognosis of patients is poor. Patients with high-risk factors may benefit from extended proximal intestinal resection (>10 cm) to avoid residual positive PCN, thereby reducing local recurrence.

AIM: To observe the early retinal degeneration and activation of microglia in C57BL/6N(Crb1rd8/rd8)mice.METHODS:Totally 15 male SPF C57BL/6N mice and 15 male SPF C57BL/6J mice were raised normally, and fundus photography examinations were performed by Micron-Ⅲ at the time of 0, 4, 8, 12 wk of enrollment to calculate the number and area of retinopathy. At the end of experiment, all mice were sacrificed and the right eyeballs were removed to prepare retinal tissue slices. After HE staining, the retinal tissue morphology was observed under optical microscope while the location and level of CX3CR1 expression were detected in immunohistochemical staining. The left eyeballs were removed to isolate retina, then Western-Blot was used to analyze the expression of CD86 and CD206 proteins in retina, and the concentration of IL-1β, IL-6, TNF-α, IL-4 and IL-10 in retina was detected by electrochemiluminescence.RESULTS:The result of fundus photography examinations showed that the number of retinopathy in the C57BL/6N significantly increased at 4, 8, and 12 wk, and there were differences in variations compared with the C57BL/6J at the same time point(all P<0.05). In the changes in area of retinopathy, there was a difference between two groups at 12 wk(P<0.05), but no difference in variations within groups(both P>0.05). HE staining of retinal tissue showed that the retinal structure of C57BL/6N mice was abnormal, with loose and disordered cell arrangement, and the photoreceptor layer was obviously protruding to the inner side of retina with a drusen-like protrusion. The retinal structure of C57BL/6J mice was clearer, with orderly cell arrangement and no obvious abnormality. Immunohistochemical results showed that CX3CR1 was highly expressed in ganglion cell layer, inner and outer plexiform layer, photoreceptor cell layer and lesion in the retina of C57BL/6N mice, with a mean density of 0.285±0.056 in C57BL/6N and 0.189±0.084 in C57BL/6J mice(P<0.05). The results of Western-Blot showed that the expression of CD86 and CD206 in retina of C57BL/6N increased compared with that in C57BL/6J to varying degrees, and the difference of CD86 was statistically significant(P<0.05). The results of cytokine detection showed that the level of IL-1β, TNF-α in C57BL/6N was significantly higher than that of C57BL/6J, while IL-10 was significantly lower(all P<0.05).CONCLUSION: The retinal degeneration of C57BL/6N(Crb1rd8/rd8)mice progressed slowly and gradually aggravated with age. The retinal structure of the lesion was disordered and accompanied by microglial infiltration dominated by M1 polarization.

Objective To propose a classification method for ultrasound images of pedicle screw canals based on radiomics analysis,and to evaluate the integrity of the screw canal.Methods With thoracolumbar spine specimens from 4 fresh cadavers,50 pedicle screw canals were pre-established and ultrasound images of the canals were acquired.A total of 2 000 images(1 000 intact and 1 000 damaged canal samples)were selected.The dataset was randomly divided in a 4∶1 ratio using 5-fold cross-validation to form training and testing sets(consisting of 1 600 and 400 samples,respectively).Firstly,the optimal radius of the region of interest was identified using the Otsu's thresholding method,followed by feature extraction using pyradiomics.Principal component analysis and the least absolute shrinkage and selection operator algorithm were employed for dimensionality reduction and feature selection,respectively.Subsequently,3 machine learning models(support vector machine[SVM],logistic regression,and random forest)and 3 deep learning models(visual geometry group[VGG],ResNet,and Transformer)were used to classify the ultrasound images.The performance of each model was evaluated using accuracy.Results With a region of interest radius of 230 pixels,the SVM model achieved the highest classification accuracy of 96.25%.The accuracy of the VGG model was only 51.29%,while the accuracies of the logistic regression,random forest,ResNet,and Transformer models were 85.50%,80.75%,80.17%,and 75.18%,respectively.Conclusion For ultrasound images of pedicle screw canals,the machine learning model performs better than the deep learning model as a whole,and the SVM model has the best classification performance,which can be used to assist physicians in diagnosis.

Medical Physics is an interdiscipline which is formed by applying the basic principles, methods, and techniques of physics to clinical medical research such as prevention, diagnosis, and treatment of human diseases, and it is a compulsory professional basic course for medical students. However, there are many medical students reflect that the content of this course is obscure and difficult to understand. Teaching effect is not ideal. The main reasons are that the teaching method is single and the reference materials are few. Based on the actual situation of the course, Hebei Medical University, China promotes formative evaluation from the content of teaching materials, teaching means, and other aspects. At the same time, by combining with the Internet, the digital construction has been realized, deepening the reform of the Medical Physics curriculum, and remarkable results have been achieved.

At present, surgical resection remains as the main treatment for patients with colorectal cancer (CRC). Alongside the progress in oncologic surgical technique, minimally invasive approaches, such as laparoscopy and transanal total mesorectal excision (taTME), and individualized surgical options, such as lateral lymph node dissection and multivisceral resection, the patient mortality associated with traditional surgical approaches has been improved. Neoadjuvant therapy can decrease local recurrence and distant metastasis, and improve the survival of patients. The optimization of adjuvant therapy shortens treatment cycle, reduces treatment risk and toxicities. Recently, neoadjuvant immunotherapy has become the new standard of the treatment for mismatch repair-deficient or microsatellite instability high CRC. However, it shows unsatisfactory outcomes in patients with mismatch repair-proficient/microsatellite stable CRC, which needs overcoming the limi-tation of CRC genephenotype. With more researches on CRC, the more biomarkers predicting the response to treatment will be found and the novel comprehensive treatment of CRC will be developed, which will make the treatment of CRC more individualized and accurate, and finally benefit more patients.

Lateral lymph node metastasis (LLNM) is one of the major causes for post-operative local recurrence of middle and low rectal cancer. At present, there are still controversies on the diagnosis and treatment of LLNM. The radiological assessment of LLNM generally relies on morphological criteria such as the size or shape of the node or the response to therapy, in which the diagnostic accuracy of MRI is superior to that of other imaging techniques. Neoadjuvant chemoradiotherapy could not achieve good local control for suspicious LLNM. Lateral lymph node dissection (LLND) can reduce tumor local recurrence significantly, but the clinical value of LLND in survival and quality of life of patients has been questioned. 4K laparoscope can decrease the incidence of perioperative complications and urinary and sexual dysfunction to a certain extent. Thus, selective LLND should be undertaken to patients with suspicious LLNM after neoadjuvant chemoradiotherapy, in order to reduce tumor local recurrence and improve the prognosis of patients. The authors elaborate on diagnosis and treatment including surgery or chemoradiotherapy of LLNM in 4K laparoscopic surgery for middle and low rectal cancer combined with their own experiences.

Lateral lymph node metastasis (LLNM) is the main metastatic mode and the major cause of locoregional recurrence of mid-low rectal cancer. Single chemoradiotherapy cannot achieve good local control for LLNM, while the argument against performing lateral lymph node dissection (LLND) is the increased rate of urinary and sexual dysfunction after surgery. Ultra-high definition surgical field and delicate resolution by 4K laparoscopic surgical system will be helpful to achieve good tumor clearance and function preservation by identification and exposure of the important anatomic structures such as pelvic autonomic nerve and internal iliac vessels. Therefore, selective LLND can reduce local recurrence rates, particularly in the pelvic sidewall. LLND with autonomic nerve preservation by 4K laparoscopic system is expected to further decrease the risk of perioperative complications and urinary and sexual dysfunction in appropriate patients with neoadjuvant chemoradiotherapy.