Thiolated pectin nanoparticles: Preparation, characterization and ex vivo corneal permeation study

The objective of present study was to prepare thiolated pectin nanoparticles and to evaluate them for ocular delivery. Thiolated pectin nanoparticles were prepared by ionotropic-gelation technique using magnesium chloride as the ionic cross-linker and timolol maleate as the model drug. The results revealed that increasing the concentration of magnesium chloride results in significant increase in particle size, while % entrapment is decreased significantly by increase in the concentration of thiolated pectin. The optimal formulation having particle size of 237 nm and % entrapment of 94.6% was obtained at concentrations of thiolated pectin - 0.01% (w/v) and magnesium chloride - 0.01% (w/v). On comparative evaluation, thiolated pectin nanoparticulate formulation provided significantly higher ex vivo corneal permeation of timolol maleate across the excised goat cornea than the conventional aqueous solution.     

Role of calcium and cyclophilin D in the regulation of mitochondrial permeabilization induced by glutathione depletion

The mitochondrial permeability transition (MPT) is a calcium and oxidative stress sensitive transition in the permeability of the mitochondrial inner membrane that plays a crucial role in cell death. However, the mechanism regulating the MPT remains controversial. To study the role of oxidative stress in the regulation of the MPT, we used diethyl maleate (DEM) to deplete glutathione (GSH) in human leukemic CEM cells. GSH depletion increased mitochondrial calcium and reactive oxygen species (ROS) levels in a co-dependent manner causing loss of mitochondrial membrane potential (deltapsi(m)) and cell death. These events were inhibited by the calcium chelator BAPTA-AM and the antioxidants N-acetylcysteine (NAC) and the triphenyl phosphonium-linked ubiquinone derivative MitoQ. In contrast, the MPT inhibitor cyclosporine A (CsA) and small interference RNA (siRNA) knockdown of cyclophilin D (Cyp-D) were not protective. These results indicate that mitochondrial permeabilization induced by GSH depletion is not regulated by the classical MPT.     

罗格列酮对胰岛素抵抗高血压大鼠主动脉功能的影响

为探讨罗格列酮(rosiglitazone,ROSI)对胰岛素抵抗高血压大鼠(insulin resistant-hypertensive rats,IRHR)主动脉功能的影响及其可能机制,用高果糖饲养Sprague-Dawley大鼠8周,制备IRHR模型,并通过相关指标的检测判断造模是否成功。随后采用血管环灌流方法,观察各实验组动物离体胸主动脉环对新福林(L-phenylephrine,PE)、氯化钾(KCl)的收缩反应和对乙酰胆碱(acetylcholine,ACh)、硝普钠(sodium nitroprusside,SNP)的舒张反应：以及用一氧化氮合酶(nitric oxide synthase,NOS)的抑制剂N-硝基-L-精氨酸甲酯(N^ω-nitro-L-arginine methyl ester,L-NAME)预孵育血管30min后,主动脉环对ACh的舒张反应：同时对各实验组血清一氧化氮(nitric oxide,NO)的含量进行测定。结果显示：(1)罗格列酮能降低IRHR的收缩压、血清胰岛素水平,改善胰岛素抵抗。(2)高果糖组动物主动脉对PE、KCl的收缩反应明显增强,对ACh的舒张反应明显减弱,ROSI可逆转上述作用。(3)用L-NAME预处理后,高果糖组动物主动脉对ACh的舒张反应进一步减弱,ROSI可部分对抗上述作用。(4)各组大鼠离体主动脉对SNP的舒张反应无显著性差异。(5)ROSI对对照组大鼠主动脉功能的影响不明显。(6)与对照组相比,高果糖组动物血清NO含量显著降低,用ROSI处理后,血清NO含量显著增加。上述结果表明,ROSI能改善IRHR主动脉的舒张功能,其作用的机制可能是部分通过NOS途径促进内皮NO释放,或是通过降低血压、血清胰岛素水平,以及改善胰岛素抵抗等作用,导致血管舒张。     

A possible mechanism for an interaction between postreplication recombination repair and base misincorporation in mutation induction by N-methyl-N′-nitro-N-nitrosoguanidine in Haemophilus influenzae

Evidence in previous publications has suggested that treatment with monofunctional alkylating agents such as N-methyl-N′-nitro-nitroguanidine (MNNG) results in gaps being left in the DNA synthesized shortly after the treatment. This paper presents further evidence that suggests, though it does not conclusively prove, that there are indeed gaps. It shows that these events increase linearly with MNNG concentration, that they are formed mainly in DNA synthesized during the first hour after treatment, and that only a few are formed at later times. An hypothesis that involves the conversion by recombination repair of a single-strand base substitution, resulting from insertion of an incorrect base opposite an alkylated base, to a double-strand base substitution is proposed. It is suggested that most single-strand substitutions are removed by mismatch repair, leaving the double-strand substitutions as the main source of mutations. This hypothesis predicts that the mutation frequency will increase as the square of the exposure to MNNG, and this seems to be the case, at least at lower exposures at which complicating factors such as lengthened expression time are avoided. It also can explain a number of earlier observations on mutation fixation as detected by transformation. An attempt to show that the non-coding lesions causing the gaps were apurinic sites was unsuccessful.     

Effect of cellular glutathione depletion on cadmium-induced cytotoxicity in human lung carcinoma cells

The effect of glutathione depletion on cellular toxicity of cadmium was investigated in a subpopulation (T27) of human lung carcinoma A549 cells with coordinately high glutathione levels and Cd⁺⁺-resistance. Cellular glutathione levels were depleted by exposing the cells to diethyl maleate or buthionine sulfoximine. Depletion was dose-dependent. Exposure of the cells to 0.5 mM diethyl maleate for 4 hours or to 10 mM buthionine sulfoximine for 8 hours eliminated the threshold for Cd⁺⁺ cytotoxic effect and deccreased the LD_50S. Cells that were pretreated with 0.5 mM diethyl maleate or 10 mM buthionine sulfoximine and then exposed to these same concentrations of diethyl maleate or buthionine sulfoximine during the subsequent assay for colony forming efficiency produced no colonies, reflecting an enhanced sensitivity to these agents at low cell density. Diethyl maleate was found to be more cytotoxic than buthionine sulfoximine. Synergistic cytotoxic effects were observed in the response of diethyl maleate pretreated cells exposed to Cd⁺⁺. Thus the results demostrated that depletion of most cellular glutathione in A549-T27 cells prior to Cd⁺⁺ exposure sensitizes them to the agent's cytotoxic effects. Glutathione thus may be involved in modulating the early cellular Cd⁺⁺ cytotoxic response. Comparison of reduced glutathione levels and of Cd⁺⁺ cytotoxic responses in buthionine sulfoximine-treated A549-T27 cells with those levels in other, untreated normal and tumor-derived cells suggests that the higher level of glutathione in A549-T27 is not the sole determinant of its higher level of Cd⁺⁺ resistance.Abbreviations BSO DL-buthionine-(R,S)-sulfoximine - DEM diethyl maleate - DMSO dimethyl sulfoxide - GSH reduced glutathione - MT metallothionein     

Enalapril maleate affects 2-oxoglutarate metabolism in mitochondria from the rat kidney cortex

Enalapril maleate (EM) is the salt of N-{(S)-1-(ethoxycarbonyl)-3-phenylpropyl}-L -alanyl-L -proline, used therapeutically as an anti-hypertensive agent. The effects of EM on some aspects of the energy metabolism and membrane properties of mitochondria from rat liver and kidney cortex were studied, but only the latter were significantly affected. With 0·8 mM of EM and 2-oxoglutarate as oxidizable substrate for isolated mitochondria from rat kidney cortex, the findings were: (a) inhibition of the respiratory rate in state III (37 per cent) and decrease (45 per cent) in respiratory control ratio (RCR), with only one addition of ADP; (b) reinforcement of the inhibition when a second addition of ADP was made; (c) no significant effect either on the rate of respiration in state IV or on the ADP/O ratio; (d) no effect on the ATPase activity of mitochondria from liver or kidney cortex; (e) inhibition of the transmembrane potential (Δψ) after a second addition of ADP; (f) inhibition of the 2-oxoglutarate dehydrogenase complex. It is suggested that in kidney mitochondria, EM interferes in the gluconeogenesis dependence of at least five substrates: 2-oxoglutarate, glutamine, glutamate, lactate, and pyruvate. Also EM may inhibit Na⁺/H⁺ exchange causing natriuresis.     

The Synthesis of Moraprenyl and Dolichyl Hydrogen Succinates and Maleates

The reactions of moraprenol and dolichol with succinic and maleic anhydrides in the presence of pyridine or triethylamine were studied, and the conditions were found for the efficient synthesis of moraprenyl and dolichyl hydrogen succinates and maleates. These may be of interest as analogues of moraprenyl and dolichyl hydrogen phosphates with modified anionic groups.