荧光法研究血清白蛋白与药物的结合作用

本文应用荧光光谱法,观测了药物分子头孢菌素Ⅳ、异烟肼、维生素B_6和氟哌酸对白蛋白荧光的猝灭。由Lineweaver-Burk双倒数作图法,确定了药物与白蛋白作用的离解常数。并通过Forster偶极-偶极无辐射能量转移机理确定了药物分子氟哌酸在人血清白蛋白中与色氨酸残基之间的距离R为2.55nm,由这一距离确定了药物分子可能进入的区域和位置。     

Delivery of cytotoxic drugs from carrier cells to tumour cells by apoptosis

A new drug delivery approach, apoptotic-induced drug delivery (AIDD), is presented that is based on apoptosis as a mechanism to trigger delivery of drugs from carrier cells. It was investigated whether apoptotic drug-loaded carrier cells could deliver drugs to tumour cells by various mechanisms, including drug release through a more permeable apoptotic cell membrane, and by phagocytosis of drug-loaded apoptotic cells by tumour cells. The feasibility of this novel concept was evaluated in an in vitro carrier cell model that consisted of S49 mouse lymphoma cells that apoptose upon exposure to dexamethasone (DX). Membrane permeability was evaluated by measurement of release of a fluorescent dye (calcein-AM, C-AM) from C-AM-loaded S49 cells. Phagocytotsis of fluorescent PKH-26-labeled S49 cells was determined in co-culture studies with rat glioma (RG-2) cells using fluorescence microscopy and flow cytometry. Cytotoxicity of RG-2 cells due to temozolomide (TMZ)-loaded S49 cells was evaluated by a colony formation assay following co-culture of these cells for up to 8h. Calcein release from S49 cells was enhanced by approximately 30% at 48h following treatment with DX compared to control S49 cells. Based on both flow cytometric and microscopic analyses, RG2 phagocytized apoptotic S49 cells to a four- to sevenfold greater extent than control S49 cells at co-incubation times from 4–48h. The TMZ-loaded apoptotic S49 cells caused the largest degree of toxicity, about 50% cell kill, whereas TMZ-loaded control S49 caused 30% cell kill. The preliminary data suggest that AIDD should be further explored. This revised version was published online in June 2006 with corrections to the Cover Date.     

糖皮质激素快速抑制牛蛙椎旁神经节B细胞快兴奋性突触后电位

用单个方波电刺激牛蛙离体椎旁经节前纤维,细胞内记录节后Ｂ细胞快兴奋性突后电位,观察糖皮质激素对Ｂ细胞ｆ－ＥＰＳＰ的快速抑制作用。结果发现,ＧＣ灌注３ｍｉｎ,。Ｂ细胞ｆ－ＥＰＳＰ的幅值减小,撤除ＧＣ后,ＥＰＳＰ的幅值恢复到对照水平。作用具有剂量信赖性。     

Effect of substrate stiffness on proliferation and differentiation of periodontal ligament stem cells

Objectives

The aim of this study was to understand the effect of substrate stiffness (a mechanical factor of the extracellular matrix) on periodontal ligament stem cells (PDLSCs) and its underlying mechanism.

Materials and methods

Elastic substrates were fabricated by mixing 2 components, a base and curing agent in proportions of 10:1, 20:1, 30:1 or 40:1. PDLSC morphology was observed using scanning electron microscopy (SEM). Cell proliferation and differentiation were assessed after PDLSCs was cultured on various elastic substrates. Data were analysed using one‐way ANOVA.

Results

SEM revealed variations in the morphology of PDLSCs cultured on elastic substrates. PDLSC proliferation increased with substrate stiffness (P < .05). Osteogenic differentiation of PDLSCs was higher on stiff substrates. Notch pathway markers were up‐regulated in PDLSCs cultured on stiff substrates.

Conclusions

Results suggested that the osteogenic differentiation of PDLSCs might be promoted by culturing them in a stiffness‐dependent manner, which regulates the Notch pathway. This might provide a new method of enhancing osteogenesis in PDLSCs.

     

Revealing the Inhibitory Effect of Ginseng on Mitochondrial Respiration through Synaptosomal Proteomics

Ginseng, the active ingredients of which are ginsenosides, is the most popular herbal medicine and has potential merit in the treatment of cerebral disorders. To better understand the function of Ginseng in the cerebral system, we examined changes in the protein expression profiles of synaptosomes extracted from the cerebral cortical and hippocampal tissues of rats administered a high or low dose of Ginseng for 2 weeks. More than 5000 proteins belonging to synaptosomes were simultaneously identified and quantitated by an approach combining tandem mass tags with 2D liquid chromatography‐mass spectrometry (LC‐MS). Regarding differentially expressed proteins, downregulated proteins were much more highly induced than upregulators in the cerebral cortical and hippocampal synaptosomes, regardless of the dose of Ginseng. Bioinformatic analysis indicated the majority of the altered proteins to be located in the mitochondria, directly or indirectly affecting mitochondrial oxidative respiration. Further functional experiments using the substrate‐uncoupler inhibitor titration approach confirmed that three representative ginsenosides were able to inhibit oxidative phosphorylation in mitochondria. Our results demonstrate that Ginseng can regulate the function of mitochondria and alter the energy metabolism of cells, which may be useful for the treatment of central nervous disorders.     

Pan‐Cancer analyses of Necroptosis‐Related genes as a potential target to predict immunotherapeutic outcome

Necroptosis is a unique programmed death mechanism of necrotic cells. However, its role and specific mechanism in cancer remain unclear, and a systematic pan‐cancer analysis of necroptosis is yet to be conducted. Thus, we performed a specific pan‐cancer analysis using The Cancer Genome Atlas and Genotype‐Tissue Expression databases to analyse necroptosis expression in terms of cancer prognosis, DNA methylation status, tumour mutative burden, microsatellite instability, immune cell infiltration in different types of cancer and molecular mechanisms. For the first time, we explored the correlation between necroptosis and immunotherapy prognosis. Thus, our study provides a relatively comprehensive understanding of the carcinogenicity of necroptosis in different types of cancer. It is suggested that necroptosis can be used to evaluate the sensitivity of different patients to immunotherapy and may become a potential target for tumour immunotherapy.     

Preparation and characterization of a soluble nitrate reductase from Azotobacter chroococcum

Summary The assimilatory nitrate reductase of the N₂-fixing bacterium Azotobacter chroococcum has been prepared in a soluble form from cells grown with nitrate as the nitrogen source, and some of its properties (electron donors and cofactors, K _mvalues for substrates, molecular weight, inhibitors, activators, etc.) have been studied. The enzyme is of an inducible nature and can exist in two interconvertible forms, either active or inactive.Tungstate very efficiently inhibits growth of the microorganism in media with nitrate. When either nitrite or ammonia are substituted for nitrate as the nitrogen source, growth is unaffected by tungstate concentrations which otherwise completely suppress growth on nitrate. Tungstate interferes by decreasing the cellular level of nitrate reductase activity, preventing, as a consequence, utilization of nitrate.