5种外源物质对干旱胁迫下笔筒树幼苗生长的缓解效应北大核心CSCD

为探究外源物质对干旱胁迫下笔筒树生长的缓解效应和生理机制,对实验室培养的笔筒树幼苗进行了自然干旱胁迫,期间分别叶面喷施1.0 mmol/L水杨酸(SA)、150μmol/L褪黑素(MT)、100 mg/L多效唑(PP_(333))、2.5 mmol/L氯化钙(CaCl_(2))以及0.3 mg/L的2,4-表油菜素内酯(EBR)溶液,测定各处理幼苗的生长和光合作用、抗氧化酶、渗透调解物质等相关生理指标。结果表明:(1)与正常生长对照(CK)相比,干旱胁迫(DCK)显著抑制笔筒树幼苗地上部分的生长,但能够显著促进地下部分的生长;干旱胁迫显著抑制笔筒树叶片抗氧化酶活性,加剧对细胞膜的损害,进而引起幼苗叶片相对电导率和丙二醛含量显著上升,显著增加渗透调节物质的积累;干旱胁迫也使叶片叶绿素含量显著降低,不能正常进行光合作用,其净光合速率、气孔导度和蒸腾速率都显著降低。(2)与DCK处理相比,叶面喷施外源物质可以显著提高笔筒树幼苗叶片抗氧化酶活性,有效清除细胞内过多的活性氧,显著降低相对电导率和丙二醛含量,使细胞膜系统代谢正常,减轻干旱胁迫对笔筒树幼苗造成的伤害,并提高净光合速率、气孔导度、蒸腾速率和叶绿素含量,有效减轻干旱胁迫对光合作用的抑制。(3)隶属函数法综合评价表明,适宜浓度的水杨酸(SA)和褪黑素(MT)处理对笔筒树幼苗干旱胁迫的缓解效应最好。     

First demonstration of the neuroepithelial cells and their chemical code in the accessory respiratory organ and the gill of the sharptooth catfish,Clarias gariepinus: A preliminary study

Available studies that have examined O₂ sensing in fish have indicated that oxygen-sensitive neuroepithelial cells (NECs) are O₂ sensors in the gills and initiate cardiorespiratory reflexes in aquatic vertebrates. This is the first study describing the occurrence of NECs in accessory respiratory organs in the air-breathing catfish Clarias gariepinus. Immunocytochemical stainings with specific neuronal markers such as nNOS, VAchT, 5-HT and TH have been shown to be very useful for location and distribution of these cells in the gill fans and suprabranchial chamber that take origin from the transformation of the gill tissue. But the response of these putative O₂ chemoreceptors, their role in the respiratory reflexes and their innervation await investigation.     

Recent advancement in the discovery and development of COX-2 inhibitors: Insight into biological activities and SAR studies (2008–2019)

Cyclooxygenase-2 is a very important physiological enzyme playing key roles in various biological functions especially in the mechanism of pain and inflammation, among other roles, making it a molecule of high interest to the pharmaceutical community as a target. COX 2 enzyme is induced only during inflammatory processes or cancer and reflects no role in the guarding stomach lining. Thus, selective COX-2 inhibition can significantly reduce the adverse effects including GI tract damage and hepatotoxic effects of traditional NSAIDs like aspirin, ibuprofen, etc. Recent developments on COX-2 inhibitors is primarily focused on improving the selectivity index of the drug towards COX-2 along with enhancing the potency of the drug by modifying the scaffolds of Coxibs currently in the market like Celecoxib, Indomethacin, Oxaprozin, etc. We have reported the progress on new COX-2 inhibitors in the last decade (2008–2019) focussing on five heterocyclic rings- Pyrazole, Indole, Oxazole, Pyridine and Pyrrole. The addition of various moieties to these core rings and their structure-activity relationship along with their molecular modelling data have been explored in the article. This review aims to aid medicinal chemists in the design and discovery of better COX-2 inhibitors constructed on these five heterocyclic pharmacophores.     

Quorum sensing: an emerging link between temperature and membrane biofouling in membrane bioreactors

Lab-scale membrane bioreactors (MBRs) were investigated at 12, 18, and 25?°C to identify the correlation between quorum sensing (QS) and biofouling at different temperatures. The lower the reactor temperature, the more severe the membrane biofouling measured in terms of the transmembrane pressure (TMP) during filtration. More extracellular polymeric substances (EPSs) that cause biofouling were produced at 18?°C than at 25?°C, particularly polysaccharides, closely associated with QS via the production of N-acyl homoserine lactone (AHL). However, at 12?°C, AHL production decreased, but the release of EPSs due to deflocculation increased the soluble EPS concentration. To confirm the temperature effect related to QS, bacteria producing AHL were isolated from MBR sludge and identified as Aeromonas sp., Leclercia sp., and Enterobacter sp. through a 16S rDNA sequencing analysis. Batch assays at 18 and 25?°C showed that there was a positive correlation between QS through AHL and biofilm formation in that temperature range.     

In vivo priming of natural killer T cells by dendritic cells pulsed with hepatoma-derived acid-eluted substances

Many murine tumor cells express not only individual haplotype-matched class I MHC molecules, but also species-specific CD1d molecules. The former class I MHC molecules generally present internally synthesized tumor-derived peptide antigens to highly specific CD8⁺ cytotoxic T lymphocytes (CTLs) in acquired immunity. In contrast, the latter CD1d molecules may present tumor-associated glycolipid antigens to broadly crossreactive natural killer T (NKT) cells, which might correlate with controlling tumor metastasis. Here, we showed that murine hepatoma cell line Hepa1-6-derived acid-eluted substances might contain both D^b class I MHC-restricted antigens and CD1d-restriced substances, which could sensitize not only syngeneic bone marrow-derived DCs (BM-DCs), but also allogeneic BM-DCs expressing haplotype-mismatched class I MHC and species-specific CD1d molecules. To our surprise, intravenous (i.v.) immunization of C57BL/6 mice with the former syngeneic BM-DCs carrying acid-eluted materials primed both CD4^–CD8^– and CD8⁺ NKT cells in the spleen, whereas immunization with the latter allogeneic BM-DCs loaded the tumor-derived substances primed CD4^–CD8^–, but not CD8⁺ NKT cells. The findings shown in the present study will open a new area for cancer immunotherapy using allogeneic DCs and tumor-derived acid-eluted substances.Abbreviations CTLs cytotoxic T lymphocytes - NKT natural killer T - BM-DCs bone marrow-derived dendritic cells - CTM complete T-cell medium - FCS fetal calf serum - MMC mitomycin C - TCRs T cell receptors     

ent-Labdane glycosides from the aquatic plant Potamogeton lucens and analytical evaluation of the lipophilic extract constituents of various Potamogeton species

Two new ent-labdane glycosides, one known furano-ent-labdane and a new hydroxylated fatty acid were isolated from the dichloromethane extract of the freshwater aquatic plant Potamogeton lucens. The new compounds were assigned the structures of beta-d-glucopyranosyl-8(17),13-ent-labdadien-16,15-olid-18-oate, 18-beta-d-glucopyranosyloxy-8(17),13-ent-labdadien-16,15-olide and 13(R)-hydroxy-octadeca-(9Z,11E,15Z)-trien-oic acid by spectroscopic means. The algicidal activity of these compounds was tested against Raphidocelis subcapitata. Based on our previous study of Potamogeton pectinatus, other constituents were identified in P. lucens by LC-UV-MS, LC-NMR and GC-MS. The lipophilic extract profiles of both species are presented. Two other species, Potamogeton perfoliatus and P. crispus, were also investigated by analytical comparison of their non-polar extracts. The distribution of ent-labdanes characterized in Potamogeton is summarized.     

Metal-humic complexes and plant micronutrient uptake: a study based on different plant species cultivated in diverse soil types

There are several studies in the literature dealing with the effect of metal-humic complexes on plant metal uptake, but none of them correlate the physicochemical properties of the complexes with agronomic results. Our study covers both aspects under various experimental conditions. A humic extract (SHE) obtained from a sapric peat was selected for preparing the metal–humic complexes used in plant experiments. Fe–, Zn– and Cu–humic complexes with a reaction stoichiometry of 2:0.25 (humic:metal, w/w) were chosen after studying their stability and solubility with respect to pH (6–9) and the humic:metal reaction stoichiometry. Wheat and alfalfa plants were greenhouse cultured in pots containing one of three model soils: an acid, sandy soil and two alkaline, calcareous soils. Treatments were: control (no additions), SHE (53 mg kg^–1 of SHE), and metal (Cu, Zn and Fe)–SHE complexes (2.5 and 5 mg kg^–1 of metal rate and a SHE concentration to make 53 mg kg ^–1). Cu- and Zn–humic complexes significantly (p0.05) increased the plant uptake and the DTPA-extractable soil fraction of complexed micronutrients in most plant–soil systems. However, these effects were associated with significant increases (p0.05) of shoot and root dry weight only in alfalfa plants. In wheat, significant increases of root and shoot dry matter were only observed in the Cu–humic treated plants growing in the acid soil, where Cu deficiency was more intense. The Fe–humic complex did not increase Fe plant assimilation in any plant–soil system, but SHE increased Fe-uptake and/or DTPA-extractable soil Fe in the wheat–calcareous soil systems. These results, taken together with those obtained from the study of the pH- and SHE:metal ratio-dependent SHE complex solubility and stability, highlight the importance of the humic:Fe complex stoichiometry on iron bioavailability as a result of its influence on complex solubility.     

Patterns of divergence in the effects of mating on female reproductive performance in flour beetles

Sexual selection can lead to rapid divergence in reproductive characters. Recent studies have indicated that postmating events, such as sperm precedence, may play a key role in speciation. Here, we stress that other components of postmating sexual selection may be involved in the evolution of reproductive isolation. One of these is the reproductive investment made by females after mating (i.e., differential allocation). We performed an experiment designed to assess genetic divergence in the effects of mating on female reproductive performance in flour beetles, Tribolium castaneum. Females were mated to males of three different wild-type genotypes at two different frequencies, in all possible reciprocal combinations. Male genotype affected all aspects of female reproduction, through its effects on female longevity, total offspring production, reproductive rate, mating rate, and fertility. Moreover, male and female genotype interacted in their effects on offspring production and reproductive rate. We use the pattern of these interactions to discuss the evolutionary process of divergence and suggest that the pattern is most consistent with that expected if divergence was driven by sexually antagonistic coevolution. In particular, the fact that females exhibited a relatively weak response to males with which they were coevolved suggests that females have evolved resistance to male gonadotropic signals/stimuli.     

Characterization of the adhesive mucilages secreted by live diatom cells using atomic force microscopy

Atomic Force Microscopy (AFM) resolved the topography and mechanical properties of two distinct adhesive mucilages secreted by the marine, fouling diatom Craspedostauros australis. Tapping mode images of live cells revealed a soft and cohesive outer mucilage layer that encased most of the diatom's siliceous wall, and force curves revealed an adhesive force of 3.58 nN. High loading force, contact mode imaging resulted in cantilever 'cleaned' cell walls, which enabled the first direct observation of the active secretion of soft mucilage via pore openings. A second adhesive mucilage consisted of strands secreted at the raphe, a distinct slit in the silica wall involved in cell-substratum attachment and motility. Force measurements revealed a raphe adhesive strand(s) resistant to breaking forces up to 60 nN, and these strands could only be detached from the AFM cantilever probe using the manual stepper motor.