[Performance of loop-mediated isothermal amplification (LAMP) assay for detection of Schistosoma japonicum infection in Oncomelania snails in schistosomiasis transmission-interrupted regions]

OBJECTIVE

To compare the effectiveness of loop-mediated isothermal amplification (LAMP) assay and microscopic examinations for detection of Schistosoma japonicum infections in Oncomelania hupensis in transmission-interrupted regions, so as to provide insights into the optimization of snail surveillance tools in these regions.

METHODS

Four hilly schistosomiasis-endemic villages where transmission interruption was achieved were selected in Heqing County of Yunnan Province as the study villages, including Xinzhuang and Gule villages in hilly regions and Lianyi and Yitou villages in dam regions. Snail survey was performed by means of systematic sampling combined with environmental sampling in July 2018. All captured snails were identified for S. japonicum infections using microscopy. In addition, 10 to 20 snails were randomly sampled from each snail habitat following microscopy, numbered according to environments and subjected to LAMP assay. The positive rate of settings with S. japonicum-infected snails was compared among villages.

RESULTS

A total of 7 949 living snails were captured from 83 snail habitats in 4 villages, and no S. japonicum infection was detected in snails. There were 226 mixed samples containing 1 786 snails subjected to LAMP assay, and positive LAMP assay was found in 3 mixed samples from 3 snail habitats in 2 dam villages. The positive rates of settings with S. japonicum-infected snails were comparable between Lianyi Village (one setting) and Yitou Village (2 set tings) (5.89% vs. 14.29%, P = 0.344). However, the overall positive rate of settings with S. japonicum-infected snails was significantly higher in dam villages (9.67%, 3/31) than in hilly villages (0) (P = 0.048).

CONCLUSIONS

LAMP assay is more sensitive to detect S. japonicum infections in O. hupensis than conventional microcopy method, which may serve as a supplementary method for detection of S. japonicum infections in O. hupensis in high-risk snail habitats in hilly transmission-interrupted regions.

A novel compact heat exchanger using gap flow mechanism

A novel, compact gap-flow heat exchanger (GFHE) using heat-transfer fluid (HTF) was developed in this paper. The detail design of the GFHE coaxial structure which forms the annular gap passage for HTF is presented. Computational fluid dynamics simulations were introduced into the design to determine the impacts of the gap width and the HTF flow rate on the GFHE performance. A comparative study on the GFHE heating rate, with the gap widths ranged from 0.1 to 1.0 mm and the HTF flow rates ranged from 100 to 500 ml/min, was carried out. Results show that a narrower gap passage and a higher HTF flow rate can yield a higher average heating rate in GFHE. However, considering the compromise between the GFHE heating rate and the HTF pressure drop along the gap, a 0.4 mm gap width is preferred. A testing loop was also set up to experimentally evaluate the GFHE capability. The testing results show that, by using 0.4 mm gap width and 500 ml/min HTF flow rate, the maximum heating rate in the working chamber of the as-made GFHE can reach 18 °C/min, and the average temperature change rates in the heating and cooling processes of the thermal cycle test were recorded as 6.5 and 5.4 °C/min, respectively. These temperature change rates can well satisfy the standard of IEC 60068-2-14:2009 and show that the GFHE developed in this work has sufficient heat exchange capacity and can be used as an ideal compact heat exchanger in small volume desktop thermal fatigue test apparatus.

Lentivirus-mediated knockdown of NOB1 suppresses the proliferation of colon cancer cells

NOB1 is important for ribosome biogenesis and protein degradation. Previous studies showed that it could regulate the growth and colony-formation ability of ovarian, breast and hepatocellular carcinoma cells. However, its function in colon cancer cells is largely unknown. In this study, we found that NOB1 could express in 6 different colon cancer cell lines. Lentivirus-mediated shRNA targeted NOB1 could suppress the endogenous gene expression. NOB1 depletion significantly inhibited cell proliferation and colony formation ability, as determined by MTT and colony formation assays. Flow cytometry analysis showed NOB1 silencing arrested cell cycle in G0 / G1 phase. Moreover, the percentage of cells at sub-G1 phase dramatically increased after NOB1 knockdown. These results indicate that NOB1 may play an important role in the growth and tumorigensis of colon cancer and knockdown of NOB1 may be a potential therapeutic method for colon cancer in the future.