Has the Integrated Medical Insurance System promoted return-to-hometown entrepreneurship among migrant workers? Evidence from China.

An important way to reduce urban-rural disparity lies in encouraging migrant workers to return to their hometowns for entrepreneurship. This paper examines the effect of the Integrated Medical Insurance System on the return-to-hometown entrepreneurship among migrant workers. Using microdata from the China Household Finance Survey (CHFS) spanning from 2013 to 2019, we find that the Integrated Medical Insurance System (IMIS) significantly increases the likelihood of migrant workers returning to their hometowns for entrepreneurship by 0.44%. This result remains stable after a series of robustness checks. Heterogeneity results indicate that this "pullback effect" is more pronounced for those who are male and with lower educational levels, higher income, larger social networks, and lower risk preferences. Finally, the interaction between the Mass Entrepreneurship and Innovation policy (MEI) and IMIS can create a more significant combined effect in promoting the return of migrant workers to their hometowns for entrepreneurial activities.

[Characteristics of climate change and its impacts on water resources in Qilian Mountains, China]. / ç¥è¿žå±±æ°”å€™å˜åŒ–ç‰¹å¾åŠå ¶å¯¹æ°´èµ„æºçš„å½±å“.

Qilian Mountains, is an important ecological function area, an important ecological security barrier, the river runoff region in Northwest China, as well as a sensitive area to global climate change and fragile area of ecological environment. The ecological environment in this area played an important role in the economic development of Northwest China. Based on the observation data of temperature and precipitation in Qilian Mountains, MOD10A2 snow products and the flow data of Shiyang River, Heihe River and Shule River, we systematically analyzed the characteristics of climate change from 1961 to 2020, and the impacts of climate change on water resources under the scenario of climate warming. The results showed that, from 1961 to 2020, the annual average temperature increased significantly, with the rate reaching 0.39 ℃·(10 a)-1. The warming rate was the highest in the western part of Qilian Mountains, followed by the middle and eastern regions. The warming trend was the strongest in winter and the lowest in spring. The average temperature changed abruptly in 1997. The annual average precipitation increased with flucturation, with a rate of 10 mm·(10 a)-1, which increased most obviously in the middle of Qilian Mountains. After 2004, it entered a rainy period, with a warm and humid trend. The precipitation in the four seasons showed an increasing trend and the increase of precipitation in summer contributed the most to the annual precipitation. Annual precipitation was dominated by interannual scale change, and the contribution rate of 2.8-year was approximately 64.3%. The snow cover of Qilian Mountains was obviously affected by temperature and snowfall, which was negatively correlated with summer temperature and positively correlated with snowfall. From 2016 to 2020, the temperature increase had slowed down in Qilian Mountains, the snowfall had increased, and the snow cover tended to increase. After 2000, the temperature and precipitation increased more obviously, the meltwater from glacier and snow increased, the mountainous runoff of Shiyang River, Heihe River and Shule River had an increasing trend. Our findings are of great significance to the construction of ecological civilization and coping with climate change in Qilian Mountains.

Assessment of Pig-a, Micronucleus, and Comet Assay Endpoints in Tg.RasH2 Mice Carcinogenicity Study of Aristolochic Acid I.

A newly developed in vivo Pig-a gene mutation assay displays great potential for integration into genotoxicity tests. To obtain more evidence for application of the Pig-a assay, we integrated this assay, micronucleus test in peripheral blood (MN-pb test) and bone marrow (MN-bm test), as well as a Comet assay into a transgenic RasH2 mice carcinogenicity study. Fourteen male RasH2 mice and five wild-type (WT) mice were treated with a strong mutagen aristolochic acid I at a dose of 5 mg/kg/day for 4 consecutive weeks. Mice recovered in 5 weeks. Peripheral bloods were collected for Pig-a assay, MN-pb test, and Comet assay at several time points, while bone marrow and target organs were harvested for the MN-bm test and pathological diagnosis after mice were euthanized. Finally, 13 of the 14 RasH2 mice developed squamous cell carcinomas in the forestomach, while there were no carcinomas in the WT mice. Pig-a mutant frequencies (MFs) consecutively increased throughout the study to a maximum value of approximately 63-fold more than background. These frequencies were relative to the incidence, size, and malignant degree of tumors. Micronucleated reticulocytes increased from Day 1 to Day 49, before returning to background levels. No positive responses were observed in either the MN-bm test or the Comet assay. Results suggested that, when compared with the other two tests, the Pig-a assay persistently contributed to sustaining MFs, enhanced detection sensitivity due to the accumulation of Pig-a mutations, and demonstrated better predictability for tumorigenicity. Environ. Mol. Mutagen. 61:266-275, 2020. © 2019 Wiley Periodicals, Inc.

Genotoxicity assessment of melamine in the in vivo Pig-a mutation assay and in a standard battery of assays.

The genotoxicity of melamine was evaluated with the combined Pig-a mutation/micronucleus assay, the bacterial reverse mutation assay, and the in vitro cytokinesis-block micronucleus assay (CBMN). Five groups of six- to eight-week-old male Sprague-Dawley (SD) rats were given three daily doses of vehicle control (100% pure sesame oil), melamine (500, 1000, and 2000 mg/kg) or positive control (N-ethyl-N-nitrosourea, ENU, 20 mg/kg) by oral gavage. Peripheral blood was sampled pre-dose (day -1) and at time points up to day 60. Pig-a mutant frequencies were determined in total red blood cells (RBCs) and reticulocytes (RETs) as RBC(CD59-) and RET(CD59-) frequencies, on days -1, 15, 29 and 60, and micronucleus frequencies were measured in RETs on day 4. No significant increases in RBC(CD59-) or RET(CD59-) frequencies were observed for the melamine-treated group at any of the time points studied, but the positive control, ENU, induced statistically significant increases compared with the vehicle control. Similar results were obtained in the micronucleus assay. Melamine did not induce statistically significant increases in %MN-RET. In the bacterial reverse mutation assay, melamine was tested from 62.5 to 1000 µg/plate in tester strains TA97a, TA98, TA100, TA102, and TA1535, with and without metabolic activation, and no evidence of toxicity or mutagenicity was observed at any dose tested. In the in vitro CBMN assay, in Chinese hamster ovary (CHO) cells, melamine was tested (75, 150, and 300 µg/mL) in the presence and absence of S9 mix, and no positive increases in the number of cells containing micronuclei were seen. These results suggest that melamine does not exhibit significant genotoxic potential. These data could be valuable for risk assessment purposes and also for further characterizing the new in vivoPig-a gene mutation assay.

Assessment of 5-fluorouracil and 4-nitroquinoline-1-oxide in vivo genotoxicity with Pig-a mutation and micronucleus endpoints.

Genotoxicity assessments were conducted on male Sprague Dawley rats treated with 5-fluorouracil (5-FU) and 4-nitroquinoline-1-oxide (4NQO) as part of an international validation trial of the Pig-a mutant phenotype assay. Rats were orally exposed to 0, 11.5, 23, or 46 mg/kg/day 5-FU for three consecutive days (Days 1-3); blood was sampled on Days -1, 4, 15, 29, and 45. Pig-a mutant phenotype reticulocyte (RET(CD59-)) and mutant phenotype erythrocyte (RBC(CD59-)) frequencies were determined on Days -1, 15, 29, and 45, and percent micronucleated reticulocytes (%MN-RET) were measured on Day 4. Rats were treated with 4NQO for 28 consecutive days by oral gavage, at doses of 1.5, 3, or 6 mg/kg/day. RBC(CD59-) and RET(CD59-) frequencies were determined on Days -1, 15, and 29, and MN-RET were quantified on Day 29. Whereas 5-FU was found to increase %MN-RET, no significant increases were observed for RBC(CD59-) or RET(CD59-) at any of the time points studied. The high dose of 4NQO (6 mg/kg/day) was observed to markedly increase RBC(CD59-) and RET(CD59-) frequencies, and this same dose level caused a weak but significantly elevated increase in MN-RET (approximately twofold). Collectively, the results provide additional support for the combination of Pig-a mutation and MN-RET into acute and 28-day repeat-dose studies.