Effects of elevated atmospheric ammonia concentration on photosynthetic characteristics and grain yield in wheat under different nitrogen rates.

To evaluate the effects of nitrogen (N) application rates on the growth, photosynthetic traits and yield of winter wheat under elevated atmospheric ammonia (NH3) concentrations could provide guidance for N management under high NH3 environment. We conducted a split-plot experiment for two consecutive years (2020-2021 and 2021-2022) with top-open chambers. The treatments included two NH3 concentrations [elevated ambient NH3 concentration at 0.30-0.60 mg·m-3 (EAM) and air NH3 concentration at 0.01-0.03 mg·m-3 (AM)] and two N application rates [recommended N dose (+N) and no N application (-N)]. We analyzed the effects of aforementioned treatments on net photosynthetic rate (Pn), stomatal conductance (gs), chlorophyll content (SPAD value), plant height, and grain yield. The results showed that averaged across the two years, EAM significantly increased Pn, gs, and SPAD values at the jointing and booting stages at the -N level by 24.6%, 16.3%, 21.9% and 20.9%, 37.1%, 5.7%, respectively, compared with AM. However, EAM significantly decreased Pn, gs, and SPAD values at jointing and booting stages at +N level by 10.8%, 5.9%, 3.6% and 6.8%, 18.9%, 9.3%, respectively, over AM treatment. There was a significant effect of NH3 treatment, N application rates and their interaction on plant height and grain yield. Compared with AM, EAM increased the average plant height and grain yield by 4.5% and 32.1% at -N level and decreased by 1.1% and 8.5% at +N level, respectively. In a nutshell, the eleva-ted ambient NH3 concentration had positive effect on photosynthetic characteristics, plant height, and grain yield under ambient N condition, but a inhibitory effect under N application.

Mycobacterium vaccae Nebulization in the Treatment of COVID-19: A Randomized, Double-Blind, Placebo-Controlled Trial.

Background: Severe acute respiratory syndrome coronavirus 2 infection is associated with strong infectiousness and has no effective therapy. We aimed to explore the efficacy and safety of Mycobacterium vaccae nebulization in the treatment of Coronavirus Disease 2019 (COVID-19). Methods: In this randomized, double-blind, placebo-controlled clinical trial, we included 31 adult patients with moderate COVID-19 who were admitted to the Fourth People's Hospital of Nanning (Nanning, China) between January 22, 2020 and February 17, 2020. Patients were randomly divided into two groups: group A (standard care group) and group B (M. vaccae in combination with standard care group). The primary outcome was the time interval from admission to viral RNA negative conversion (oropharyngeal swabs were used in this study). Secondary outcomes included chest computed tomography (CT), mortality, length of hospital stay, complications during treatment, and so on. Patients were followed up to 4 weeks after discharge (reexamination of viral RNA, chest CT, etc.). Results: Nucleic acid test negative conversion time in group B was shorter than that in group A (2.9 days [2.7-8.7] vs. 6.8 days [3.3-13.8]; p = 0.045). No death and no conversion to severe or critical cases were observed in both groups. Two weeks after discharge, neither "relapse" nor "return to positive" cases were found. Four weeks after discharge, it was found that there was no case of " relapse " or "return to positive" in group B, and 1 patient in group A showed "return to positive", but there was no clinical manifestation and imaging progression. No adverse reactions related to M. vaccae were found during observation period. Conclusion:M. vaccae treatment might shorten the time interval from admission to viral RNA negative conversion, which might be beneficial to the prevention and treatment of COVID-19. Clinical Trial Registration: ChiCTR2000030016.

Degradable Chitosan-Collagen Composites Seeded with Cells as Tissue Engineered Heart Valves.

BACKGROUND: Degradable collagen-chitosan composite materials have been used to fabricate tissue engineered heart valves. The aims of this study were to demonstrate that the collagen-chitosan composite scaffolds are cytocompatible, and endothelial cells can be differentiated from bone marrow mesenchymal stem cells (BMSCs) when seeded onto the scaffolds. The adhesion and biological activities of the seeded cells were also investigated. METHODS: Collagen-chitosan composite material was used as the cell matrix, and smooth muscle cells, fibroblasts and BMSCs were used as seed cells. After four weeks of in vitro culture, the smooth muscle cells, fibroblasts, and BMSCs were sequentially seeded into the collagen-chitosan composite material. After four weeks in culture, the cellular density and activity were assessed on segments of the tissue engineered heart valve scaffolds to determine the cell viability and proliferation in the collagen-chitosan composite material. RESULTS: The tissue engineered heart valves stained positively for both smooth muscle actin and endothelial cell factor VIII, suggesting that the seeded cells were in fact smooth muscle cells, fibroblasts, and endothelial cells. The 6-ketone prostaglandin content, as measured by radioimmunoassay, of the collagen-chitosan cell culture fluid was higher than that of the serum-free medium (P <0.01). Light and electron microscopy showed that the seeded cells had shapes similar to the morphology of smooth muscle cells, fibroblasts, and endothelial cells. CONCLUSIONS: Endothelial cells can be differentiated from BMSCs when seeded onto the collagen-chitosan composite scaffolds. The seeded cells retained their biological activity after being cultured in vitro and seeded into the collagen-chitosan composite material.