Applicability of new spin trap agent, 2-diphenylphosphinoyl-2-methyl-3,4-dihydro-2H-pyrrole N-oxide, in biological system

Electron spin resonance using spin-trapping is a useful technique for detecting direct reactive oxygen species, such as superoxide (). However, the widely used spin trap 2,2-dimethyl-3,4-dihydro-2H-pyrrole N-oxide (DMPO) has several fundamental limitations in terms of half-life and stability. Recently, the new spin trap 2-diphenylphosphinoyl-2-methyl-3,4-dihydro-2H-pyrrole N-oxide (DPhPMPO) was developed by us. We evaluated the biological applicability of DPhPMPO to analyze in both cell-free and cellular systems. DPhPMPO had a larger rate constant for and formed more stable spin adducts for than DMPO in the xanthine/xanthine oxidase (X/XO) system. In the phorbol myristate acetate-activated neutrophil system, the detection potential of DPhPMPO for was significantly higher than that of DMPO (k_DMPO = 13.95 M⁻¹ s⁻¹, k_DPhPMPO = 42.4 M⁻¹ s⁻¹). These results indicated that DPhPMPO is a potentially good candidate for trapping in a biological system.     

Ruthenium(II) complexes possessing the η-p-cymene ligand

Complexes possessing a soft donor η⁶-arene and hard donor acetylacetonate ligand, [(η⁶-p-cymene)Ru(κ²-O,O-acac-μ-CH)]₂[OTf]₂ (1) (OTf = trifluoromethanesulfonate; acac = acetylacetonate) and {Ar′ = 3,5-(CF₃)-C₆H₃}, were prepared and fully characterized. The lability of the μ-CH linkage for complex 1 and the THF ligand of 2 allow access to the unsaturated cation [(η⁶-p-cymene)Ru(κ²-O,O-acac)]⁺. The reaction of with KTp {Tp = hydridotris(pyrazolyl)borate} produces . The azide complex forms upon reaction of with N₃Ar (Ar = p-tolyl), and reaction of with CHCl₃ at 100 °C yields the chloride-bridged binuclear complex . The details of solid-state structures of [(η⁶-p-cymene)Ru(κ²-O,O-acac-μ-CH)]₂[OTf]₂ (1), and are disclosed.     

Maillard reaction of ribose 5-phosphate generates superoxide and glycation products for bovine heart cytochrome c reduction

Ribose 5-phosphate (R5P) is a sugar known to undergo the Maillard reaction (glycation) at a rapid rate. In a reaction with the lysines of bovine heart cytochrome c, R5P generates superoxide () that subsequently reduces ferri-cytochrome c to ferro-cytochrome c. The rate equation for the observed cytochrome c reduction is first order in respect to cytochrome c and half order in respect to R5P. The addition of amines to the cytochrome c-R5P system greatly increases the generation with rates of approximately 1.0 μM min⁻¹ being observed with millimolar levels of R5P and amine at 37 °C. Pre-incubation of R5P with the amine prior to cytochrome c addition further enhances the rate of cytochrome c reduction approximately twofold for every 30 min of incubation. While clearly accounting for a portion of the reduction of cytochrome c, is not the sole reductant of the system as the use of superoxide dismutase only partially limits cytochrome c reduction, and the contribution of proportionally decreases with longer amine-R5P incubation times. The remainder of the cytochrome c reduction is attributed to either the Amadori product or a cross-linked Schiff base created when a Maillard reaction-derived dicarbonyl compound(s) reacts with the amine. It is believed that these compounds directly transfer electrons to ferri-cytochrome c and subsequently become stable free-radical cations. ATP, a putative regulator of cytochrome c activity, does not inhibit electron transport from or the cross-linked Schiff base but does prevent R5P from reacting with surface lysines to generate superoxide. The spontaneous reaction between R5P and amines could serve as an alternative system for generating in solution.     

Trypanosoma cruzi: Biodistribution of technetium-99m pertechnetate in infected rats

With the aim of investigating the biodistribution of technetium-99 m pertechnetate () in rats infected with Y strain of Tripanosoma Cruzi, at the peak of parasitemia, (14th day of infection), we injected Wistar rats with 0.1 ml of (3.7 MBq). After 60 min, the percentage of radioactivity per gram was counted in several isolated organs and blood, using a gamma counter (1470 Wizard, PerkinElmer Finland). The uptake of increased significantly in blood and decreased in the colon of infected animals (p < 0.05). A significant reduction in serum iron and red blood cells and a significant increase in total proteins, leukocytes and lymphocytes in the infected rats were observed, compared with controls (p < 0.05). A reduction in muscle layer thickness of the colon and mononuclear inflammation were observed. These results conclusively demonstrate that T. cruzi infection would be associated with changes in the biodistribution of and in colon morphology, with potential clinical implications.     

Superoxide scavenging activity of pirfenidone-iron complex

Pirfenidone (PFD) is focused on a new anti-fibrotic drug, which can minimize lung fibrosis etc. We evaluated the superoxide () scavenging activities of PFD and the PFD-iron complex by electron spin resonance (ESR) spectroscopy, luminol-dependent chemiluminescence assay, and cytochrome c reduction assay. Firstly, we confirmed that the PFD-iron complex was formed by mixing iron chloride with threefold molar PFD, and the complex was stable in distillated water and ethanol. Secondary, the PFD-iron complex reduced the amount of produced by xanthine oxidase/hypoxanthine without inhibiting the enzyme activity. Thirdly, it also reduced the amount of released from phorbor ester-stimulated human neutrophils. PFD alone showed few such effects. These results suggest the possibility that the scavenging effect of the PFD-iron complex contributes to the anti-fibrotic action of PFD used for treating idiopathic pulmonary fibrosis.     

Ribosomal frameshifting in response to hypomodified tRNAs in Xenopus oocytes

We used Xenopus oocytes as an intracellular system to study ribosomal frameshifting. Microinjection of oocytes with a construct encoding the naturally occurring UUU or AAC codon at the frameshift site demonstrated that the level of frameshifting was similar or lower than found normally in retroviral frameshifting in mammalian cells, suggesting that oocytes are a reliable system to study this event. Phenylalanine (Phe) or asparagine (Asn) tRNAs with and without the highly modified wyebutoxine (Y) or queuosine (Q) base, respectively, were microinjected to assess their ability to promote frameshifting. inhibited the level of frameshifting, while promoted frameshifting providing evidence that the hypomodified form does not act only to enhance frameshifting, but is an essential requirement. Both and were used indiscriminately in frameshifting, whether the frameshift site contained the wild-type AAC, or the mutant AAU codon, suggesting that Q base modification status does not influence this process.     

Trypanosoma cruzi: Immunological predictors of benznidazole efficacy during experimental infection

C3H/HeN male mice were infected with a lethal population of Trypanosoma cruzi and treated with benznidazole (Bz). Parasitemia, body weight and survival rate were registered during the therapy with significant improvement for T. cruzi-infected Bz-treated animals. Besides, flow cytometry resulted a useful method to discriminate between cured animals from those not cured by monitoring IgG₁ bound to live trypomastigotes levels. At the end of Bz therapy, the LT splenocyte compartment was studied for activation/memory cell surface markers ( and ). Cytofluorometric analysis showed that T. cruzi-infected untreated mice increased their activated LT numbers and this effect was completely abolished only in cured mice at the end of Bz administration. The same behavior was observed for the memory LT subpopulation correlating to an effector memory () displayed by T. cruzi infection. Bz treatment was able to modulate the immunological response by reducing the deleterious effect of the acute phase in all T. cruzi-infected mice.     

The new helical zigzag chain {[Ag(Pepy)(NO3)]}∞ and mononuclear [HPepy(FeCl4)] with 3D network based on hydrogen bonds as well as π-π interactions

The title complexes, {[Ag(Pepy)(NO₃)]}_∞ (1) and [HPepy(FeCl₄)] (2) (Pepy = trans-2-(2-phenylethyleneyl)pyridine), had been synthesized and characterized structurally by single-crystal X-ray diffraction analysis, FTIR as well as thermal analysis. The geometrical structure of complex 1 is a one-dimensional helical zigzag chain. Each Ag^I center is five-coordinated by two anions and one Pepy ligand while the anion is an uncommon tetra-dentate coordinating to two Ag^I by O atoms, respectively. The anions connecting with Ag^I as bridge blocks resulted in the formation of crystalline of helical polymeric chain. In the mononuclear complex 2, the Fe^III center is four-coordinated by four Cl⁻ as [FeCl₄]⁻ anion, which connected with hydrogen atoms from the protonated N atom and the C atoms from HPepy⁺ to form multivalent hydrogen bonded network through N-H?Cl and C-H?Cl interactions. The two frameworks can be both considered as a 3D structure driven by diverse hydrogen bonds as well as π-π stacking interactions.     

From individual behaviour to population models: a case study using swimming algae

Trajectories of swimming algae are analysed, and two random-walk models developed to link the individual-level behaviour of cells to population-level advection-diffusion models for the spatial-temporal distribution of cells. The models are both of the advection-diffusion form but are based on two different sets of assumptions about the underlying random-walk behaviours, a velocity jump behaviour and a velocity diffusion behaviour. The mathematical models were developed to allow for an arbitrary (non-weak) bias in the random walk and a variable swimming speed in order to represent the experimental data. For the algal species considered, Heterosigma akashiwo, the mean upward swimming speed was computed as , and the calculated diffusion constants ranged from 2×10³ to depending on the details of the models. That two widely used modelling approaches yield substantially different population-level predictions when applied to the same empirical data suggests that better theoretical tools are needed for identifying adequate approximations for behavioural characteristics.