A novel, “hidden” penicillin-induced death of staphylococci at high drug concentration,occurring earlier than murosome-mediated killing processes

In log-phase cells of staphylococci, cultivated under high, non-lytic concentrations of penicillin G, there occurred a novel killing process hitherto hidden behind seemingly bacteriostatic effects. Two events are essential for the apprearance of this hidden death: (i) the failure of the dividing cell to deposit enough fibrillar cross-wall material to be welded together, and (ii) a premature ripping up of incomplete cross walls along their splitting system. Hidden death started as early as 10–15 min after drug addition, already during the first division cycle. It was the consequence of a loss of cytoplasmic constituents which erupted through peripheral slit-like openings in the incomplete cross walls. The loss resulted either in more or less empty cells or in cell shrinkage. These destructions could be prevented by raising the external osmotic pressure. In contrast, the conventional non-hidden death occurred only much later and exclusively during the second division cycle and mainly in those dividing cells, whose nascent cross walls of the first division plane had been welded together. These welding processes at nascent cross walls, resulting in tough connecting bridges between presumptive individual cells, were considered as a morphogenetic tool which protects the cells, so that they can resist the otherwise fatal penicillin-induced damages for at least an additional generation time (morphogenetic resistance system). Such welded cells, in the virtual absence of underlying cross-wall material, lost cytoplasm and were killed via ejection through pore-like wall openings or via explosions in the second division plane and after liberation of their murosomes, as it was the case in the presence of low, lytic concentrations of penicillin. Bacteriolysis did not cause any of the hitherto known penicillin-induced killing processes.Dedicated to Prof. Dr. Georg Henneberg on the occasion of his 85th birthday     

基于炎症免疫调节探讨艾拉莫德联合硫酸羟氯喹治疗类风湿关节炎的疗效及作用机制

摘要 目的：基于炎症免疫调节探讨艾拉莫德联合硫酸羟氯喹治疗类风湿关节炎（RA）的疗效及作用机制。方法：选择2021年4月~2023年3月期间武汉科技大学附属天佑医院和武汉市第四医院收治的120例RA患者。根据随机数字表法将患者分为对照组和研究组,每组各为60例。对照组接受硫酸羟氯喹治疗,研究组接受艾拉莫德联合硫酸羟氯喹治疗。对比两组疗效、临床症状缓解时间、炎症因子[肿瘤坏死因子α（TNF-α）、白细胞介素-6（IL-6）、干扰素α（IFN-α）、干扰素-γ（IFN-γ）]、视觉疼痛模拟评分（VAS）和简易健康生活质量评分（SF-36）、免疫因子[T淋巴细胞亚群（CD4⁺、CD8⁺、CD4⁺/CD8⁺）、免疫球蛋白（Ig）G、IgM、IgA]。同时观察两组用药安全性。结果：与对照组相比,研究组的临床总有效率更高（P<0.05）。研究组的关节疼痛、关节肿胀、关节晨僵缓解时间均短于对照组（P<0.05）。治疗6个月后,两组TNF-α、IL-6、IFN-γ、IFN-α下降,且研究组低于对照组（P<0.05）。治疗6个月后,两组CD8⁺升高,且研究组高于对照组;CD4⁺、CD4⁺/CD8⁺降低,且研究组低于对照组（P<0.05）。治疗6个月后,两组IgG、IgM、IgA下降,且研究组低于对照组（P<0.05）。治疗6个月后,两组VAS评分下降,且研究组低于对照组;SF-36评分升高,且研究组高于对照组（P<0.05）。两组不良反应发生率组间对比未见差异（P>0.05）。结论：艾拉莫德联合硫酸羟氯喹治疗RA,疗效确切,能缩短临床症状缓解时间,缓解关节疼痛和提高患者生活质量,且用药安全、副作用少,其作用机制可能与调节炎症反应、免疫反应有关。     

疲劳引起的轻度认知功能障碍的诊疗研究进展

疲劳引起的包括易受到无关信息的干扰、工作错误率增加,任务检测能力和策略性行为调整的能力下降等表现,属轻度认知功能障碍(MCI)范畴。本文对疲劳引起的轻度认知功能障碍的中西医研究进展进行整理。从其涉及的神经生理学机制、中医对其病因病机的认识、中西医特色治疗方面进行了总结,并结合高新技术发展趋势对其生理学机制研究及诊疗的发展进行展望,为今后的研究提供新思路。     

Evidence for the mechanism of the irreversible inhibition of oestrone sulphatase (ES) by aminosulphonate based compounds

In our search for the mechanism of the enzyme oestrone sulphatase (ES) we have synthesised and evaluated a number of compounds that were predicted to possess some inhibitory activity. Some of these compounds were indeed found to be inhibitors of ES, whilst other compounds were not. From a consideration of the structure–activity relationship (SAR) of the inhibitors and non-inhibitors of this enzyme, we discovered a factor which we now believe is the main inhibitory moiety within the aminosulphonated inhibitors. We therefore report the results of our study into a series of phenyl and alkyl sulphamated compounds as inhibitors of ES. The results of the study show that the substituted phenyl sulphamates are potent inhibitors, whereas the alkyl compounds are, in general, non-inhibitors. Using the results of our SAR study, we postulate the probable mechanism for the irreversible and reversible inhibition of ES, and rationalise the role of the different physicochemical factors in the inhibition of this crucial enzyme.     

Mutational Analysis of the Integral Membrane Methyltransferase Isoprenylcysteine Carboxyl Methyltransferase (ICMT) Reveals Potential Substrate Binding Sites

The eukaryotic integral membrane enzyme isoprenylcysteine carboxyl methyltransferase (ICMT) methylates the carboxylate of a lipid-modified cysteine at the C terminus of its protein substrates. This is the final post-translational modification of proteins containing a CAAX motif, including the oncoprotein Ras, and therefore, ICMT may serve as a therapeutic target in cancer development. ICMT has no discernible sequence homology with soluble methyltransferases, and aspects of its catalytic mechanism are unknown. For example, how both the methyl donor S-adenosyl-l-methionine (AdoMet), which is water-soluble, and the methyl acceptor isoprenylcysteine, which is lipophilic, are recognized within the same active site is not clear. To identify regions of ICMT critical for activity, we combined scanning mutagenesis with methyltransferase assays. We mutated nearly half of the residues of the ortholog of human ICMT from Anopheles gambiae and observed reduced or undetectable catalytic activity for 62 of the mutants. The crystal structure of a distantly related prokaryotic methyltransferase (Ma Mtase), which has sequence similarity with ICMT in its AdoMet binding site but methylates different substrates, provides context for the mutational analysis. The data suggest that ICMT and Ma MTase bind AdoMet in a similar manner. With regard to residues potentially involved in isoprenylcysteine binding, we identified numerous amino acids within transmembrane regions of ICMT that dramatically reduced catalytic activity when mutated. Certain substitutions of these caused substrate inhibition by isoprenylcysteine, suggesting that they contribute to the isoprenylcysteine binding site. The data provide evidence that the active site of ICMT spans both cytosolic and membrane-embedded regions of the protein.     

微生物亚硝酸盐还原酶的研究进展

亚硝酸盐还原酶(Nitrite reductase,简称NiR,EC1.7.2.1)是催化亚硝酸盐(Nitrite,简称NIT)还原的一类酶,可降解NIT为NO或NH3,是自然界氮循环过程的关键酶。本文详细阐述亚硝酸盐还原酶的分类、结构特点、催化机制以及现阶段的应用领域,为深入研究亚硝酸还原酶提供参考。     

Gold(III) compounds as anticancer agents: relevance of gold-protein interactions for their mechanism of action

Gold(III) compounds constitute an emerging class of biologically active substances, of special interest as potential anticancer agents. During the past decade a number of structurally diverse gold(III) complexes were reported to be acceptably stable under physiological-like conditions and to manifest very promising cytotoxic effects against selected human tumour cell lines, making them good candidates as anti-tumour drugs. Some representative examples will be described in detail. There is considerable interest in understanding the precise biochemical mechanisms of these novel cytotoxic agents. Based on experimental evidence collected so far we hypothesize that these metallodrugs, at variance with classical platinum(II) drugs, produce in most cases their growth inhibition effects through a variety of "DNA-independent" mechanisms. Notably, strong inhibition of the selenoenzyme thioredoxin reductase and associated disregulation of mitochondrial functions were clearly documented in some selected cases, thus providing a solid biochemical basis for the pronounced proapoptotic effects. These observations led us to investigate in detail the reactions of gold(III) compounds with a few model proteins in order to gain molecular-level information on the possible interaction modes with possible protein targets. Valuable insight on the formation and the nature of gold-protein adducts was gained through ESI MS (electrospray ionization mass spectrometry) and spectrophotometric studies of appropriate model systems as it is exemplified here by the reactions of two representative gold(III) compounds with cytochrome c and ubiquitin. The mechanistic relevance of gold(III)-induced oxidative protein damage and of direct gold coordination to protein sidechains is specifically assessed. Perspectives for the future of this topics are briefly outlined.     

Ag/TiO2纳米材料对烟曲霉的抑制作用及机制

目的 合成Ag/TiO2纳米材料,对其进行表征测定,并探讨其对烟曲霉的抑制作用及具体机制。方法 采用光催化还原法制备Ag/TiO2纳米材料,紫外可见分析和扫描电镜对其进行表征测定;微量液基稀释法检测对烟曲霉的最低抑菌浓度（MIC）,以及生物量的抑制作用;ELISA试剂盒检测对真菌谷胱甘肽还原酶、总谷胱甘肽、线粒体膜电位的影响,荧光显微镜检测活性氧的产生。结果 成功制备Ag/TiO2纳米材料,分布均匀;对烟曲霉的MIC值为0.5 μg/mL,能完全抑制烟曲霉生物量,与单独纳米银相比,具有更好的抗菌活性。机制研究发现其主要通过降低烟曲霉体内谷胱甘肽及其还原酶的含量,诱导过量活性氧的产生,最终导致线粒体膜电位降低,使真菌细胞发生凋亡。结论 Ag/TiO2纳米材料可有效阻断烟曲霉等真菌在空气中的传播,具有广泛的应用前景。     

复合污染研究的新进展

对多种污染物相互作用形成的复合污染效应的研究已成为环境科学发展的重要方向之一。本文从元机复合污染、无机－有机复合污染以及有机复合污染3个方面对复合污染效应的最新进展进行了综述,并从化学、生理学、酶学、细胞学等角度出发探计了复合污染机理,指出了复合污染研究中存在的若干问题和发展方向。     

Allosteric Regulation of the Human and Mouse Deoxyribonucleotide Triphosphohydrolase Sterile α-Motif/Histidine-Aspartate Domain-containing Protein 1 (SAMHD1)

The deoxyribonucleotide triphosphohydrolase SAMHD1 restricts lentiviral infection by depleting the dNTPs required for viral DNA synthesis. In cultured human fibroblasts SAMHD1 is expressed maximally during quiescence preventing accumulation of dNTPs outside S phase. siRNA silencing of SAMHD1 increases dNTP pools, stops cycling human cells in G₁, and blocks DNA replication. Surprisingly, knock-out of the mouse gene does not affect the well being of the animals. dNTPs are both substrates and allosteric effectors for SAMHD1. In the crystal structure each subunit of the homotetrameric protein contains one substrate-binding site and two nonidentical effector-binding sites, site 1 binding dGTP, site 2 dGTP or dATP. Here we compare allosteric properties of pure recombinant human and mouse SAMHD1. Both enzymes are activated 3–4-fold by allosteric effectors. We propose that in quiescent cells where SAMHD1 is maximally expressed GTP binds to site 1 with very high affinity, stabilizing site 2 of the tetrameric structure. Any canonical dNTP can bind to site 2 and activate SAMHD1, but in cells only dATP or dTTP are present at sufficient concentrations. The apparent K_m for dATP at site 2 is ∼10 μm for mouse and 1 μm for human SAMHD1, for dTTP the corresponding values are 50 and 2 μm. Tetrameric SAMHD1 is activated for the hydrolysis of any dNTP only after binding of a dNTP to site 2. The lower K_m constants for human SAMHD1 induce activation at lower cellular concentrations of dNTPs thereby limiting the size of dNTP pools more efficiently in quiescent human cells.