Cytoplasmic domain and enzymatic activity of ACE2 are not required for PI4KB dependent endocytosis entry of SARS-CoV-2 into host cells

The recent COVID-19 pandemic poses a global health emergency. Cellular entry of the causative agent SARS-CoV-2 is mediated by its spike protein interacting with cellular receptor-human angiotensin converting enzyme 2 (ACE2). Here, by using lentivirus based pseudotypes bearing spike protein, we demonstrated that entry of SARS-CoV-2 into host cells was dependent on clathrin-mediated endocytosis, and phosphoinositides played essential roles during this process. In addition, we showed that the intracellular domain and the catalytic activity of ACE2 were not required for efficient virus entry. Finally, we showed that the current predominant Delta variant, although with high infectivity and high syncytium formation, also entered cells through clathrin-mediated endocytosis. These results provide new insights into SARS-CoV-2 cellular entry and present proof of principle that targeting viral entry could be an effective way to treat different variant infections.     

Valuing urban green spaces in mitigating climate change: A city‐wide estimate of aboveground carbon stored in urban green spaces of China's Capital

Urban green spaces provide manifold environmental benefits and promote human well‐being. Unfortunately, these services are largely undervalued, and the potential of urban areas themselves to mitigate future climate change has received little attention. In this study, we quantified and mapped city‐wide aboveground carbon storage of urban green spaces in China's capital, Beijing, using field survey data of diameter at breast height (DBH) and tree height from 326 field survey plots, combined with satellite‐derived vegetation index at a fine resolution of 6 m. We estimated the total amount of carbon stored in the urban green spaces to be 956.3 Gg (1 Gg = 10⁹ g) in 2014. There existed great spatial heterogeneity in vegetation carbon density varying from 0 to 68.1 Mg C ha^‐1, with an average density of 7.8 Mg C ha^?1. As expected, carbon density tended to decrease with urban development intensity (UDI). Likely being affected by vegetation cover proportion and configuration of green space patches, large differences were presented between the 95th and 5th quantile carbon density for each UDI bin, showing great potential for carbon sequestration. However, the interquartile range of carbon density narrowed drastically when UDI reached 60%, signifying a threshold for greatly reduced carbon sequestration potentials for higher UDI. These findings suggested that urban green spaces have great potential to make contribution to mitigating against future climate change if we plan and design urban green spaces following the trajectory of high carbon density, but we should be aware that such potential will be very limited when the urban development reaches certain intensity threshold.     

Leptin induces insulin-like signaling that antagonizes cAMP elevation by glucagon in hepatocytes

Although many effects of leptin are mediated through the central nervous system, leptin can regulate metabolism through a direct action on peripheral tissues, such as fat and liver. We show here that leptin, at physiological concentrations, acts through an intracellular signaling pathway similar to that activated by insulin in isolated primary rat hepatocytes. This pathway involves stimulation of phosphatidylinositol 3-kinase (PI3K) binding to insulin receptor substrate-1 and insulin receptor substrate-2, activation of PI3K and protein kinase B (AKT), and PI3K-dependent activation of cyclic nucleotide phosphodiesterase 3B, a cAMP-degrading enzyme. One important function of this signaling pathway is to reduce levels of cAMP, because leptin-mediated activation of both protein kinase B and phosphodiesterase 3B is most marked following elevation of cAMP by glucagon, and because leptin suppresses glucagon-induced cAMP elevation in a PI3K-dependent manner. There is little or no expression of the long form leptin receptor in primary rat hepatocytes, and these signaling events are probably mediated through the short forms of the leptin receptor. Thus, leptin, like insulin, induces an intracellular signaling pathway in hepatocytes that culminates in cAMP degradation and an antagonism of the actions of glucagon.     

蜡梅种子抑菌成分研究

在抑菌活性追踪指导下,采用硅胶柱层析的方法。从蜡梅种子中分离得到一活性化合物A,经质谱、核磁共振波谱等技术鉴定为d－洋蜡梅碱。经杀虫活性和抑菌活性测定,该化合物对粘虫的幼虫无毒杀活性;对西瓜枯萎病菌、玉米小斑病菌、玉米大斑病菌、番茄早疫病菌均有显著的抑菌活性。其抑制中浓（EC50）分别为：3878．8、29．3、103．1、328．3mg／L,但对油菜菌核病菌无抑制活性。     

Spatial-temporal expression of pum1 and pum2 in medaka Oryzias latipes

Two pumilios, pum1 and pum2, were identified in medaka Oryzias latipes. Oryzias latipes pum1 and pum2 are ubiquitous in the adult tissues but with specific expression in the germ cells of gonads, ovary and testis. Pum1 is expressed in the spermatogonia to spermatocytes whilst pum2 presents in spermatocytes of testis only. Oryzias latipes pum1 and pum2 are maternally supplied RNA with ubiquitous expression in the early stages, and embryonic expression of pum1 and pum2 may begin from early gastrula. Both pum1 and pum2 are expressed in the tissues including brain, eye and trunk, and both are expressed in the gonads after hatching. Taken together, Pum1 and Pum2 may play important roles in embryonic and germ cell development of O. latipes.     

氯化钠密度梯度离心法制备用于显微注射的外源DNA片段

DNA显微注射是生产转基因动物最可靠和最常使用的一种方法,外源DNA的纯度对显微注射的成功起着至关重要的作用。本文介绍用氯化钠密度梯度离心的方法制备用于显微注射的外源DNA片段。与传统的琼脂糖凝胶回收的方法相比较,用此方法制备的外源DNA片段对小鼠受精卵进行显微注射后,受卵体母鼠的胚胎存活率,以及子代小鼠的外源基因整合率均有明显的提高。这一方法可为进一步提高转基因动物的成功率,提供方法学上的参考。 Abstract:DNA microinjection is the most popular and reliable method of producing transgenic animals.The purity of foreign DNA plays an important role for the success of microinjection.In this study,we introduced the use of sodium chloride step gradients in fractionating foreign DNA fragment for microinjection.The data demonstrated that,compared with the conventional agarose gel extraction method,NaCl purification scheme of toreign DNA could improve the treated embryo survival and foreign DNA intergration rate markedly.     

Noggin and bFGF cooperate to maintain the pluripotency of human embryonic stem cells in the absence of feeder layers

Human embryonic stem (hES) cells are typically maintained on mouse embryonic fibroblast (MEF) feeders or with MEF-conditioned medium. However, these xenosupport systems greatly limit the therapeutic applications of hES cells because of the risk of cross-transfer of animal pathogens. Here we showed that the bone morphogenetic protein antagonist noggin is critical in preventing differentiation of hES cells in culture. Furthermore, we found that the combination of noggin and basic fibroblast growth factor (bFGF) was sufficient to maintain the prolonged growth of hES cells while retaining all hES cell features. Since both noggin and bFGF are expressed in MEF, our findings suggest that they may be important factors secreted by MEF for maintaining undifferentiated pluripotent hES cells. Our data provide new insight into the mechanism how hES cell self-renewal is regulated. The newly developed feeder-free culture system will provide a more reliable alternative for future therapeutic applications of hES cells.