[Soil bacterial community characteristics and ecological function prediction of alfalfa and crop rotation systems in the Loess Plateau, Northwest China]. / 黄土高原苜蓿-粮食作物轮作下土壤细菌群落特征和生态功能预测.

In order to understand the effects of lucerne cropping rotation on the bacterial community of loess soil, a long-term field experiment was conducted in rain-fed agricultural area of Loess Plateau. The cropping systems included continuous lucerne (Medicago sativa, LC), lucerne removed and rotated with spring wheat (Triticum aestivum, LFW), lucerne removed and rotated with corn (Zea mays, LFC), lucerne removed and rotated with potato (Solanum tuberosum, LP), and lucerne removed and rotated with continuous millet (Panicum miliaceum, LM). Based on 16S rRNA high-throughput sequencing technology, we investigated soil bacterial community structure and diversity in different cropping systems, and predicted ecological function using PICRUSt method. The results showed that the dominant phyla of loess soil bacteria were Actinomycetes (20.3%-32.0%), Proteobacteria (19.2%-23.0%), Acidobacteria (12.4%-14.2%) and Chloroflexus (11.0%-12.7%). The dominant genus was Bacillus (1.9%) in lucerne-corn system and Pseudarthrobacter (2.5%) in other treatments. Rotation with annual crops decreased the relative abundance of Actinobacteria and increased that of Chloroflexi and Firmicutes. Redundancy analysis showed that the main soil factors driving soil bacterial community structure were nitrate, ammonium, and total nitrogen. PICRUSt function prediction results showed that metabolism (78.6%-79.1%) was the main function of soil bacterial communities in loess soil. Rotation with continued annual crops significantly decreased the abundance of soil bacterial carbohydrate metabolism functional genes, and significantly increased the abundance of functional genes for soil bacterial cofactors and vitamin metabolism, neurodegenerative diseases, and immune system. In conclusion, lucerne removed and rotated with continuous annual crops changed soil bacterial community structure and ecological functions. This study provided theoretical reference to explore succession characteristics of soil bacteria and to select succeeding crops for alfalfa in loess soil.

[Soil nematode community characteristics of alfalfa field with different growing ages in the semi-arid Loess Plateau of Central Gansu, Northwest China]. / 陇中黄土高原半干旱区不同种植年限紫花苜蓿土壤线虫群落分布特征.

To clarify the impacts of long-term alfalfa plantation on the soil nematode community, soil samples were collected from different alfalfa growing ages (2 a, 9 a, 18 a) in the semi-arid area of Loess Plateau in Central Gansu by Illumina Miseq sequencing technology. The main controlling factors affecting its community change were also explored. The results showed that soil nematode belongs to 2 classes, 7 orders, 16 families and 21 genera. Among them, Chromadorea was the dominant group (44.6%-81.4%), the relative abundance of which decreased with alfalfa growing ages. Paratylenchus, Helicotylenchus, Xiphinema, Pristionchus, Ditylenchus, Panagrolaimus, Longidorus, Aprutides, Isolaimium and Aglenchus were the special nematode species of alfalfa, among which Paratylenchus (54.1%), Helicotylenchus (23.9%) and Xiphinema (21.9%) were the dominant nematodes in 2 a, 9 a and 18 a alfalfa soil respectively. Plant-parasitic nematode was the dominant group in alfalfa soil (31.8%-67.1%), and its relative abundance decreased at first and then increased with alfalfa growing ages. Results of redundancy analysis showed that soil available phosphorus and total nitrogen were the dominant environmental factors affecting community structure of soil nematodes in the region.

Effect of Exposure to Famine during Early Life on Risk of Metabolic Syndrome in Adulthood: A Meta-Analysis.

BACKGROUND: Emerging studies have explored the association between the famine exposure during early life and the risk of the metabolic syndrome, and the results remain controversial. This meta-analysis was performed to summarize the famine effects on the prevalence of metabolic syndrome (MetS) in adulthood. Materials and Methods. We searched the PubMed, Web of Science, Embase, ScienceDirect, and Chinese National Knowledge Infrastructure for relevant studies up to December 2019. Pooled odd ratios (ORs) with 95% confidence intervals (CIs) were used to estimate the effect exposure to famine on MetS using a random-effects model, and the I 2 was used to evaluate the heterogeneity. RESULTS: The analyses included 39 studies from 10 articles with a total of 81504 participants. Fourteen studies from 10 articles for fetal famine exposure, 20 studies from 7 articles for childhood famine exposure, and 5 studies from 3 articles for adolescence/adult famine exposure were included in this meta-analysis. Compared with a nonexposed group, famine exposure significantly increased the risk of MetS for early life famine exposure (OR = 1.27, 95% CI: 1.18-1.38), fetal famine exposure (OR = 1.27, 95% CI: 1.14-1.43), and childhood famine exposure (OR = 1.29, 95% CI: 1.16-1.44). Subgroup analyses showed that the result was consistent regardless of the study designs, definitions of MetS, and causes of famine, with or without adjustment for age, smoking, drinking, and physical activity. CONCLUSIONS: This meta-analysis suggests that exposure to famine during early life may increase the risk of MetS in adulthood.

Association between cigarette smoking and the risk of dysmenorrhea: A meta-analysis of observational studies.

BACKGROUND: Emerging studies have found inconsistent results on the potential relationship between cigarette smoking and dysmenorrhea. Therefore, the aim of this study was to quantitatively synthesize the previous findings on the preceding relationship using meta-analysis. METHODS: Previous studies on the association between cigarette smoking and dysmenorrhea, published not later than November 2019, were systematically searched, using MeSH heading and/or relevant terms, in the electronic databases of PubMed, Medline, Web of Science and EMBASE. The I2 statistic was used to assess heterogeneity, whose source was explored using subgroup analysis. A pooled effect size was obtained using random effects model, and sensitivity analysis was performed to assess the consistency of the pooled effect size. RESULTS: After a rigorous screening process, 24 studies involving 27,091 participants were included in this meta-analysis. The results indicated that smokers were 1.45 times more likely to develop dysmenorrhea than non-smokers (odds ratio (OR) = 1.45, 95% confidence interval (CI): 1.30-1.61). In addition, individuals classified as currently smoking were 1.50 times more likely to develop dysmenorrhea than those who were classified as never smoking (OR = 1.50, 95% CI: 1.33-1.70), whereas being a former smoker was 1.31 times more likely to develop dysmenorrhea than being a never smoker (OR = 1.31, 95% CI: 1.18-1.46). Sensitivity analysis showed that exclusion of any single study did not materially alter the overall combined effect. CONCLUSION: The evidence from this meta-analysis indicated a significant association between cigarette smoking (both current and former smoking) and dysmenorrhea. The adverse effects of smoking provide further support for prevention of dysmenorrhea and emphasize the need to target women.