The antioxidant characteristics of medicinal plant extracts from Western Siberia

An antioxidant activity of the water-alcohol extracts of leaves of ten herbs from Western Siberia was studied. In vivo the capability of extracts to protect cells of Escherichia coli against the bacteriostatic action of H ₂O₂ and the influence of the extracts on the expression of the antioxidant gene katG coding catalase-hydroperoxidase I were investigated. In vitro the radical-binding activity with DPhPG^· (1,1-diphenyl-2-picrylhydrazyl radical), the chelating capability with ferrozine, and total composition of flavonoids and tannins were determined. The extracts of Filipendula stepposa and Limonium gmelinii were characterized by the highest antioxidant activity. According to data, the test extracts could have an antioxidant effect on bacteria in different ways at once including the direct inhibition of ROS (reactive oxygen species), iron ion chelation and antioxidant gene induction.     

Transcription Factors of Direct Neuronal Reprogramming in Ontogenesis and Ex Vivo

Molecular Biology - Direct reprogramming technology allows several specific types of cells, including specialized neurons, to be obtained from readily available autologous somatic cells. It...     

Disease modifying treatment of spinal cord injury with directly reprogrammed neural precursor cells in non-human primates

BACKGROUNDThe development of regenerative therapy for human spinal cord injury (SCI) is dramatically restricted by two main challenges: the need for a safe source of functionally active and reproducible neural stem cells and the need of adequate animal models for preclinical testing. Direct reprogramming of somatic cells into neuronal and glial precursors might be a promising solution to the first challenge. The use of non-human primates for preclinical studies exploring new treatment paradigms in SCI results in data with more translational relevance to human SCI.AIMTo investigate the safety and efficacy of intraspinal transplantation of directly reprogrammed neural precursor cells (drNPCs).METHODSSeven non-human primates with verified complete thoracic SCI were divided into two groups: drNPC group (n = 4) was subjected to intraspinal transplantation of 5 million drNPCs rostral and caudal to the lesion site 2 wk post injury, and lesion control (n = 3) was injected identically with the equivalent volume of vehicle.RESULTSFollow-up for 12 wk revealed that animals in the drNPC group demonstrated a significant recovery of the paralyzed hindlimb as well as recovery of somatosensory evoked potential and motor evoked potential of injured pathways. Magnetic resonance diffusion tensor imaging data confirmed the intraspinal transplantation of drNPCs did not adversely affect the morphology of the central nervous system or cerebrospinal fluid circulation. Subsequent immunohistochemical analysis showed that drNPCs maintained SOX2 expression characteristic of multipotency in the transplanted spinal cord for at least 12 wk, migrating to areas of axon growth cones.CONCLUSIONOur data demonstrated that drNPC transplantation was safe and contributed to improvement of spinal cord function after acute SCI, based on neurological status assessment and neurophysiological recovery within 12 wk after transplantation. The functional improvement described was not associated with neuronal differentiation of the allogeneic drNPCs. Instead, directed drNPCs migration to the areas of active growth cone formation may provide exosome and paracrine trophic support, thereby further supporting the regeneration processes.     

Chlorophyll fluorescence in the leaves of Tradescantia species of different ecological groups: Induction events at different intensities of actinic light

Chlorophyll fluorescence analysis is one of the most convenient and widespread techniques used to monitor photosynthesis performance in plants. In this work, after a brief overview of the mechanisms of regulation of photosynthetic electron transport and protection of photosynthetic apparatus against photodamage, we describe results of our study of the effects of actinic light intensity on photosynthetic performance in Tradescantia species of different ecological groups. Using the chlorophyll fluorescence as a probe of photosynthetic activity, we have found that the shade-tolerant species Tradescantia fluminensis shows a higher sensitivity to short-term illumination (≤20 min) with low and moderate light (≤200 μE m⁻² s⁻¹) as compared with the light-resistant species Tradescantia sillamontana. In T. fluminensis, non-photochemical quenching of chlorophyll fluorescence (NPQ) and photosystem II operational efficiency (parameter Φ_PSII) saturate as soon as actinic light reaches ≈200 μE m⁻² s⁻¹. Otherwise, T. sillamontana revealed a higher capacity for NPQ at strong light (≥800 μE m⁻² s⁻¹). The post-illumination adaptation of shade-tolerant plants occurs slower than in the light-resistant species. The data obtained are discussed in terms of reactivity of photosynthetic apparatus to short-term variations of the environment light.     

Proliferation and tumorigenity of murine hepatoma cells irradiated with polychromatic visible and infrared light

In experiments in vitro, the effects of polychromatic visible (VIS) light combined with polychromatic infrared light (VIS-IR, 480–3400 nm) and the effects of the entire spectrum of VIS radiation (385–750 nm) on viability and proliferative activity of the murine hepatoma cells MH22a were studied. In experiments in vivo, changes in the tumorigenic properties of cells MH22a were studied after the same kinds of light exposure. It was shown that irradiation of hepatoma cells with two kinds of polychromatic light at a wide range of doses (4.8–38.4 J/cm²) did not lead to an increase in the number of dead cells for 24–72 h of cultivation and did not cause deceleration of the hepatoma cell proliferation; moreover, the VIS-IR light at a dose of 4.8 J/cm² and the VIS light at a dose 38.4 J/cm² even promoted more intense cell proliferation after 24 h. In cells irradiated with VIS-IR and VIS light, the proliferation index rose by 1.6 and 1.4 times, respectively, and the time of the cells’ number doubling decreased as compared with control. Studying the tumorigenic properties of irradiated tumor cells has shown that, for 30 days after transplantation to syngenic mice C3HA of hepatoma cells 24 h after their irradiation with VIS-IR light at a dose of 4.8 J/cm², the tumor volume decreased significantly (2.6–4.1 times) at all periods of observation, while the incidence of tumor formation decreased, whereas the survival of the tumor-bearing mice did not change. Transplantation of cells irradiated with the same light at a dose of 9.6 J/cm² did not lead to significant changes in the tumor volume, the tumor formation incidence, and animal survival. The main contribution to the antitumor effect of VIS-IR light seems to be made by the VIS component, as transplantation into mice of cells irradiated with VIS light alone at a dose of 38.4 J/cm² also stimulating proliferation of hepatoma cells in vitro resulted in a decrease of their tumorigenic properties. However, the IR component in the combined VIS-IR radiation enhanced the antitumor effect of the VIS light; as a result, it was manifested after use of doses eight times lower (4.8 J/cm²) than in the case of VIS light alone (38.4 J/cm²). Mechanisms of the decrease of tumorigenic properties of hepatoma cells after irradiation with polychromatic light at doses stimulating their proliferation in vitro are studied.     

An exceptional irradiance-induced decrease of light trapping in two Tradescantia species: an unexpected relationship with the leaf architecture and zeaxanthin-mediated photoprotection

Leaf anatomy and irradiance-dependent leaf transmittance changes serving as irradiance acclimation mechanisms in leaves were studied in two ecologically contrasting Tradescantia species, a shade plant T. fluminensis Vell. and a sun plant T. sillamontana Matuda, grown at different irradiances. A dramatic increase in leaf thickness (2 to 4-fold) under a high growth irradiance (800 μmol m^?2 s^?1) compared with a low growth irradiance (60 μmol m^?2 s^?1), achieved mainly by expansion of the epidermis, was recorded in both species. The effect took place on the background of modest changes in mesophyll thickness (1.8-fold in T. fluminensis and 1.15-fold in T. sillamontana) and chloroplast size (0.8-fold in T. fluminensis and an insignificant change in T. sillamontana). Mesophyll structure and growth irradiance response did not seem to facilitate significantly light-dependent chloroplast (avoidance) movement in these species. Nevertheless, an exceptionally large (2 to 4-fold) irradiance-induced increase in light transmittance attributable to chloroplast avoidance movement was revealed. This increase by far exceeded that in other higher plants according to available literature. The magnitude of the irradiance-dependent transmittance changes positively correlated both with the rate of photosystem II recovery and with the extent of xanthophyll deepoxidation in the leaves. This was opposite to a negative correlation observed between the same parameters in different plant species. We hypothesize that, at the evolutionary timescale, chloroplast avoidance movement might adjust independently from other photoprotective mechanisms, e.g., non-photochemical quenching, whereas, on the ontogenetic timescale, adjustment of these mechanisms inevitably follows the same trend.     

Supramolecular structure of self-assembling alamethicin analog studied by ESR and PELDOR

Three analogs of alamethicin F50/5, labelled with the TOAC (='2,2,6,6-tetramethylpiperidin-1-oxyl-4-amino-4-carboxylic acid') spin label at positions 1 (Alm1), 8 (Alm8), and 16 (Alm16), resp., were studied by Electron-Spin-Resonance (ESR) and Pulsed Electron-Electron Double-Resonance (PELDOR) techniques in solvents of different polarity to investigate the self-assembly of amphipathic helical peptides in membrane-mimicking environments. In polar solvents, alamethicin forms homogeneous solutions. In the weakly polar chloroform/toluene 1 : 1 mixture, however, this peptide forms aggregates that are detectable at 293 K by ESR in liquid solution, as well as by PELDOR in frozen, glassy solution at 77 K. In liquid solution, free alamethicin molecules and their aggregates show rotational-mobility correlation times tau(r) of 0.87 and 5.9 ns, resp. Based on these values and analysis of dipole-dipole interactions of the TOAC labels in the aggregates, as determined by PELDOR, the average number N of alamethicin molecules in the aggregates is estimated to be less than nine. A distance-distribution function between spin labels in the supramolecular aggregate was obtained. This function exhibits two maxima: a broad one at a distance of 3.0 nm, and a wide one at a distance of ca. 7 nm. A molecular-dynamics (MD)-based model of the aggregate, consisting of two parallel tetramers, each composed of four molecules arranged in a 'head-to-tail' fashion, is proposed, accounting for the observed distances and their distribution.     

Interactions of quinone with the iron-sulfur protein of the bc(1) complex: is the mechanism spring-loaded?

Since available structures of native bc(1) complexes show a vacant Q(o)-site, occupancy by substrate and product must be investigated by kinetic and spectroscopic approaches. In this brief review, we discuss recent advances using these approaches that throw new light on the mechanism. The rate-limiting reaction is the first electron transfer after formation of the enzyme-substrate complex at the Q(o)-site. This is formed by binding of both ubiquinol (QH(2)) and the dissociated oxidized iron-sulfur protein (ISP(ox)). A binding constant of approximately 14 can be estimated from the displacement of E(m) or pK for quinone or ISP(ox), respectively. The binding likely involves a hydrogen bond, through which a proton-coupled electron transfer occurs. An enzyme-product complex is also formed at the Q(o)-site, in which ubiquinone (Q) hydrogen bonds with the reduced ISP (ISPH). The complex has been characterized in ESEEM experiments, which detect a histidine ligand, likely His-161 of ISP (in mitochondrial numbering), with a configuration similar to that in the complex of ISPH with stigmatellin. This special configuration is lost on binding of myxothiazol. Formation of the H-bond has been explored through the redox dependence of cytochrome c oxidation. We confirm previous reports of a decrease in E(m) of ISP on addition of myxothiazol, and show that this change can be detected kinetically. We suggest that the myxothiazol-induced change reflects loss of the interaction of ISPH with Q, and that the change in E(m) reflects a binding constant of approximately 4. We discuss previous data in the light of this new hypothesis, and suggest that the native structure might involve a less than optimal configuration that lowers the binding energy of complexes formed at the Q(o)-site so as to favor dissociation. We also discuss recent results from studies of the bypass reactions at the site, which lead to superoxide (SO) production under aerobic conditions, and provide additional information about intermediate states.