Characterization of the chromophores of pyoverdins and related siderophores by electrospray tandem mass spectrometry

Characteristic fragment ions of the various chromophores of the pyoverdin siderophore family obtained by collision activated dissociation of the [M+2H]²⁺ ions are reported allowing unambiguous identification. Tandem mass spectrometrical studies revealed the existence of the first example of a ferribactin with a succinamide side chain, and they add some information to the problem in which way a malic acid side chain is attached to the chromophore.     

Modifications of rat liver glucocorticoid receptor by insulin-induced hypoglycemia

Stability-, equilibrium- and kinetic binding parameters, transformation rate and sedimentation properties of liver cytosol glucocorticoid receptor from insulin-treated rats were studied. 40% elevation of cytosolic glucocorticoid binding and a lower affinity of the receptor for ligand were observed in hypoglycemic rats as compared to the controls. A small but significant decrease of [3H]triamcinolone acetonide-receptor complexes association rate and an increase of dissociation rate were also found. The rate and the extent of activation of the complexes from insulin-treated rats were somewhat higher compared to the controls, and the complexes from both groups showed higher affinity for the nuclei isolated from insulin-treated animals. Mixing experiments suggested that insulin treatment lead to alterations at the level of both the receptor protein and the nuclear binding sites. Sedimentation properties of transformed and untransformed receptor remained unchanged upon insulin treatment. The physiological relevance of the data was confirmed by hypoglycemia-related stimulation of tyrosine aminotransferase induction by dexamethasone.     

Cysteine 195 Has a Critical Functional Role in Catalysis by Isocitrate Lyase from Escherichia coli

Cysteine 195 in isocitrate lyase from Escherichia coli has been replaced by directed mutagenesis. Substitution by Ser yields enzyme with a k_cat that is 0.03% that of wild type, and substitution by Ala, Gly, Thr, or Val yields completely inactive enzyme. The present results are consistent with a functional role of Cys 195. Received: 26 March 1997 / Accepted: 29 April 1997     

Comparison of the Bacterial Composition and Structure in Symptomatic and Asymptomatic Endodontic Infections Associated with Root-Filled Teeth Using Pyrosequencing

Residual microorganisms and/or re-infections are a major cause for root canal therapy failure. Understanding of the bacterial content could improve treatment protocols. Fifty samples from 25 symptomatic and 25 asymptomatic previously root-filled teeth were collected from Sudanese patients with periradicular lesions. Amplified 16S rRNA gene (V1-V2) variable regions were subjected to pyrosequencing (FLX 454) to determine the bacterial profile. Obtained quality-controlled sequences from forty samples were classified into 741 operational taxonomic units (OTUs) at 3% dissimilarity, 525 at 5% dissimilarity and 297 at 10% dissimilarity, approximately corresponding to species-, genus- and class levels. The most abundant phyla were: Firmicutes (29.9%), Proteobacteria (26.1%), Actinobacteria (22.72%), Bacteroidetes (13.31%) and Fusobacteria (4.55%). Symptomatic patients had more Firmicutes and Fusobacteria than asymptomatic patients, while asymptomatic patients showed more Proteobacteria and Actinobacteria. Interaction of disease status and age was observed by two-way ANOSIM. Canonical correspondence analysis for age, tooth restoration and disease status showed a correlation of disease status with the composition and prevalence of different members of the microbial community. The pyrosequencing analysis revealed a distinctly higher diversity of the microbiota compared to earlier reports. The comparison of symptomatic and asymptomatic patients showed a clear association of the composition of the bacterial community with the presence and absence of symptoms in conjunction with the patients’ age.     

Oxidative toxicity in diabetes and Alzheimer’s disease: mechanisms behind ROS/ RNS generation

Reactive oxidative species (ROS) toxicity remains an undisputed cause and link between Alzheimer’s disease (AD) and Type-2 Diabetes Mellitus (T2DM). Patients with both AD and T2DM have damaged, oxidized DNA, RNA, protein and lipid products that can be used as possible disease progression markers. Although the oxidative stress has been anticipated as a main cause in promoting both AD and T2DM, multiple pathways could be involved in ROS production. The focus of this review is to summarize the mechanisms involved in ROS production and their possible association with AD and T2DM pathogenesis and progression. We have also highlighted the role of current treatments that can be linked with reduced oxidative stress and damage in AD and T2DM.     

Highly Selective Anti-Cancer Activity of Cholesterol-Interacting Agents Methyl-β-Cyclodextrin and Ostreolysin A/Pleurotolysin B Protein Complex on Urothelial Cancer Cells

Cholesterol content can vary distinctly between normal and cancer cells, with elevated levels in cancer cells. Here, we investigated cholesterol sequestration with methyl-β-cyclodextrin (MCD), and pore-formation with the ostreolysin A/pleurotolysin B (OlyA/PlyB) protein complex that binds to cholesterol/sphingomyelin-rich membrane domains. We evaluated the effects on viability of T24 invasive and RT4 noninvasive human urothelial cancer cells and normal porcine urothelial (NPU) cells. Cholesterol content strongly correlated with cancerous transformation, as highest in the T24 high-grade invasive urothelial cancer cells, and lowest in NPU cells. MCD treatment induced prominent cell death of T24 cells, whereas OlyA/PlyB treatment resulted in greatly decreased viability of the RT4 low-grade noninvasive carcinoma cells. Biochemical and transmission electron microscopy analyses revealed that MCD and OlyA/PlyB induce necrotic cell death in these cancer cells, while viability of NPU cells was not significantly affected by either treatment. We conclude that MCD is more toxic for T24 high-grade invasive urothelial cancer cells, and OlyA/PlyB for RT4 low-grade noninvasive urothelial cancer cells, and neither is toxic for NPU cells. The cholesterol and cholesterol/sphingomyelin-rich membrane domains in urothelial cancer cells thus constitute a selective therapeutic target for elimination of urothelial cancer cells.     

Assessment of biological activities of chitosan Schiff base tagged with medicinal plants

A chitosan Schiff base with an aromatic aldehyde was synthesized and characterized by FTIR and NMR spectroscopies. Furthermore, the degree of substitution was calculated based on the ratios of the area of the proton of the imine (A_imine) and the area of the peak of the proton of the pyranose ring (A_H-2). The antimicrobial activities were determined against bacterial and fungal strains, as well as multiple drug-resistant (MDR) bacteria. The chitosan Schiff base was also tagged with medicinal plants, for example, Curcuma longa, Peganum harmala, Lepidium sativam, and cruciferous vegetables, and the biological activities determined against pathogenic bacterial and fungal strains. The chitosan Schiff base showed maximum zone of inhibition of 22 mm against Staphylococcus aureus with a minimum zone of inhibition of 15 mm against Bacillus cereus. The chitosan Schiff base was fused with C longa, isothiocyanates and a combined mixture of P harmala and L sativam that has shown activities against Escherichia coli with a zone of inhibition of 28, 24, and 30 mm, respectively. The Schiff base of chitosan fused with medicinal plants also showed significant inhibitory activities against MDR bacteria.