[Advances in application of clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 system in stem cells research].

Gene engineering has attracted worldwide attention because of its ability of precise location of disease mutations in genome. As a new gene editing technology, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9) system is simple, fast, and accurate to operate at a specific gene site. It overcomes the long-standing problem of conventional operation. At the same time, stem cells are a good foundation for establishing disease model in vitro. Therefore, it has great significance to combine stem cells with the rapidly developing gene manipulation techniques. In this review, we mainly focus on the mechanism of CRISPR/Cas9 technology and its application in stem cell genomic editing, so as to pave the way for promoting rapid application and development of CRISPR/Cas9 technology.

Diffusion-weighted imaging to differentiate metastatic from non-metastatic retropharyngeal lymph nodes in nasopharyngeal carcinoma.

OBJECTIVES: To evaluate the diagnostic value of diffusion-weighted MRI for differentiating metastatic from non-metastatic retropharyngeal lymph nodes (RLNs) in patients with nasopharyngeal carcinoma (NPC). METHODS: Untreated patients with NPC (n = 145) were scanned with both morphological MRI and diffusion-weighted imaging (DWI). RLNs (n = 335) were classified as metastatic on the basis of response to therapy as assessed on follow-up MRI. Morphological (short- and long-axial diameters) and functional [mean apparent diffusion coefficient (ADC) and minimum ADC values] parameters of the RLNs were derived from DWI and compared between metastatic and non-metastatic groups. A receiver operating characteristic curve and the area under the curve were used to evaluate the effectiveness of individual criteria and to generate threshold values to diagnose RLN metastases. RESULTS: Statistically significant differences between metastatic and non-metastatic RLNs were found for all four parameters derived from DWI (p < 0.001). At threshold values, accuracies of the ADC-based criteria (0.938 and 0.965 for mean and minimum ADC values, respectively) were greater than that of size-based criteria (0.838 and 0.809 for short- and long-axial diameters). The minimum ADC value at the threshold of 0.89 × 10(-3) mm(2) s(-1) was the most effective of all parameters in differentiating metastatic from non-metastatic RLNs with the sensitivity of 95.7%, specificity of 95.1% and accuracy of 96.5%. CONCLUSIONS: DWI is feasible for differentiating metastatic RLNs from non-metastatic nodes in patients with NPC with high accuracy, and the minimum ADC derived from DWI could serve as a standard clinical marker for disease status.

[A ten years' experience with 613 mitral valve replacements].

This study was performed to assess the effect of factors on early and late mortality of isolated MVR in 613 patients. The tilting disc valve was used in 480 and the porcine xenograft bioprosthesis in 133 patients between Sep. 1978 and Nov. 1987. The overall early mortality rate was 4.89%. A comparative analysis showed that five factors (emergency operation, biventricular hypertrophy with serain, pulmonary hypertension, function class IV, and reoperation) significantly increased the early mortality rates (P less than 0.01). A 10-year follow-up study showed that the late mortality rate was significantly higher in patients with mitral insufficiency, function class IV and left ventricular hypertrophy with strain (P less than 0.01). The authors emphasize that the MVR must be performed early before the factors affecting the operative outcome are fully developed. Successive treatment with digitalis and/or diuretics should be continued in early postoperative period for 6-12 months to improve the cardiac function. Owing to the well-known durability of the bioprosthesis the authors prefer the use of mechanical valve.