典型草原大针茅种群空间格局及对长期过度放牧的响应

种群空间格局是生态学研究的基本问题之一。典型草原带由于过度放牧退化严重, 原生群落罕见, 探讨原生群落的种群空间格局具有重要生态学意义。大针茅(Stipa grandis)草原是典型草原区广泛分布的主要群落类型, 1979年围封的大针茅样地, 是目前保存完整的大针茅草原原生群落。本文选择大针茅草原原生群落和长期过度放牧群落, 应用O-Ring函数结合不同零假设模型分析了大针茅种群的空间格局。结果表明: 在原生群落中大针茅种群在小尺度范围内呈均匀分布, 而在长期过度放牧群落中则表现为聚集分布。这说明在大针茅草原原生群落中竞争是主要的相互作用, 而在长期过度放牧群落中正相互作用居主导, 验证了胁迫梯度假说; 同时证明长期过度放牧改变了种群空间格局。     

Off-the-shelf mesenchymal stem cells from human umbilical cord tissue can significantly improve symptoms in COVID-19 patients: An analysis of evidential relations

Coronavirus disease-2019 (COVID-19) has affected more than 200 countries worldwide. This disease has hugely affected healthcare systems as well as the economy to an extent never seen before. To date, COVID-19 infection has led to about 165000 deaths in 150 countries. At present, there is no specific drug or efficient treatment for this disease. In this analysis based on evidential relationships of the biological characteristics of MSCs, especially umbilical cord (UC)-derived MSCs as well as the first clinical trial using MSCs for COVID-19 treatment, we discuss the use of UC-MSCs to improve the symptoms of COVID-19 in patients.     

Identifying Primate ACE2 Variants That Confer Resistance to SARS-CoV-2

SARS-CoV-2 infects humans through the binding of viral S-protein (spike protein) to human angiotensin I converting enzyme 2 (ACE2). The structure of the ACE2-S-protein complex has been deciphered and we focused on the 27 ACE2 residues that bind to S-protein. From human sequence databases, we identified nine ACE2 variants at ACE2–S-protein binding sites. We used both experimental assays and protein structure analysis to evaluate the effect of each variant on the binding affinity of ACE2 to S-protein. We found one variant causing complete binding disruption, two and three variants, respectively, strongly and mildly reducing the binding affinity, and two variants strongly enhancing the binding affinity. We then collected the ACE2 gene sequences from 57 nonhuman primates. Among the 6 apes and 20 Old World monkeys (OWMs) studied, we found no new variants. In contrast, all 11 New World monkeys (NWMs) studied share four variants each causing a strong reduction in binding affinity, the Philippine tarsier also possesses three such variants, and 18 of the 19 prosimian species studied share one variant causing a strong reduction in binding affinity. Moreover, one OWM and three prosimian variants increased binding affinity by >50%. Based on these findings, we proposed that the common ancestor of primates was strongly resistant to and that of NWMs was completely resistant to SARS-CoV-2 and so is the Philippine tarsier, whereas apes and OWMs, like most humans, are susceptible. This study increases our understanding of the differences in susceptibility to SARS-CoV-2 infection among primates.     

Inhibition of cyclooxygenase-2 enhanced intestinal epithelial homeostasis via suppressing β-catenin signalling pathway in experimental liver fibrosis

The intestinal barrier dysfunction is crucial for the development of liver fibrosis but can be disturbed by intestinal chronic inflammation characterized with cyclooxygenase-2 (COX-2) expression. This study focused on the unknown mechanism by which COX-2 regulates intestinal epithelial homeostasis in liver fibrosis. The animal models of liver fibrosis induced with TAA were established in rats and in intestinal epithelial–specific COX-2 knockout mice. The impacts of COX-2 on intestinal epithelial homeostasis via suppressing β-catenin signalling pathway were verified pharmacologically and genetically in vivo. A similar assumption was tested in Ls174T cells with goblet cell phenotype in vitro. Firstly, disruption of intestinal epithelial homeostasis in cirrhotic rats was ameliorated by celecoxib, a selective COX-2 inhibitor. Then, β-catenin signalling pathway in cirrhotic rats was associated with the activation of COX-2. Furthermore, intestinal epithelial–specific COX-2 knockout could suppress β-catenin signalling pathway and restore the disruption of ileal epithelial homeostasis in cirrhotic mice. Moreover, the effect of COX-2/PGE2 was dependent on the β-catenin signalling pathway in Ls174T cells. Therefore, inhibition of COX-2 may enhance intestinal epithelial homeostasis via suppression of the β-catenin signalling pathway in liver fibrosis.     

Systematic study of the genus Compsilura Bouché in Southeast and East Asia with morphological and molecular data (Diptera,Tachinidae)

Compsilura concinnata (Meigen) is one of the most famous, most polyphagous and most widely distributed tachinid flies (Diptera, Tachinidae) in the world. This species is well known as a biocontrol agent of some injurious pests of cultural and wild plants and has been introduced from Europe to the United States to control mainly the gypsy moth. Recently we found three new species very closely resembling C. concinnata from Southeast and East Asia: C. lobata sp. nov. (Japan and Thailand), C. malayana sp. nov. (Malaysia) and C. pauciseta sp. nov. (Japan and Taiwan). Additionally, C. samoaensis Malloch is treated as a junior synonym of C. concinnata based on the examination of the type specimen. The genetic differences in the mitochondrial COI gene data are examined to assess the accuracy of species delimitation of Compsilura. The male postabdominal characters of these species are illustrated. The piercing female postabdomen of C. concinnata is illustrated and compared to those of other members belonging to the Blondelia group including Blondelia Robineau-Desvoidy, Celatoria Coquillett, Eucelatoria Townsend and Vibrissina Rondani.