Kinetic study of the oxidase reaction of ceruloplasmin

The effects of ionic strength, buffer composition and pH on the oxidase activity of ceruloplasmin isolated from human donor blood were studied. The steady-state kinetics of ceruloplasmin-catalyzed oxidation of organic substrates (pyrocatechine, adrenaline, rho-phenyldiamine) and Fe(II) was analyzed. The relationship between the initial reaction rate and Fe(II) concentration is described by the Michaelis--Menten kinetics, that for organic substrates--by substrate activation or by a scheme which implicates the existence of two catalytic centers in the enzyme molecule. The inhibition of adrenaline oxidation by its reaction product, adrenochrome, is competitive. The reactions studied were shown to occur via the formation of a ternary complex.     

Long-term effects of ungulates on phytophagous insects

Abstract.  1. Most plants interact with a diverse suite of herbivores, allowing the opportunity for the existence of positive and negative interactions between highly dissimilar organisms. However, most studies on herbivorous interactions have been performed under the assumption that they occur mainly between similar species. Consequently, ecologists are still far from a full understanding of the ecological factors that determine insect population dynamics.
2. In this study, a 7-year field experiment was conducted that manipulated the presence of ungulates to evaluate their effects on the abundance, attack rate, and survival of four guilds of co-occurring herbivorous insects living on the same host plant: seed predators, stem borers, gall makers and sap suckers. These four guilds differed in habits and behaviour, the first three being sessile and endophytic and the last being free-living.
3. This study shows that the abundance of all four guilds was negatively affected by ungulates. However, the effect on attack rate differed among guilds, as mammals do not affect the seed predator attack rate. Ungulates also differentially affected insect survival, ingesting only seed predators and gall makers.
4. In summary, this study suggests that diverse mechanisms may affect different insect guilds in different ways. Therefore, competition between disparate herbivores appears to be complex and can be provoked by multiple mechanisms.     

Radioresistance mechanisms of side population cells in mouse melanoma cell line B16

As we showed earlier, side population (SP) cells are more resistant to low-LET radiation than the rest of mouse melanoma B16 cells (Matchuk et al., 2012). The goal of this study was elucidation of some mechanisms of radioresistance; therefore, we analyzed the SP and non-SP cell-cycle distribution, spontaneous and radiation-induced DNA double-strand breaks (the number of γ-H2AX foci), and intracellular NO concentration. The obtained results indicate that SP cells have a significantly lower number of double-strand DNA breaks after irradiation at a dose of 3 Gy than do non-SP cells (24.4 vs. 40.3, respectively, p < 0.05, Mann-Whitney U-test). The SP cells are more quiescent than are non-SP ones (the G₁/G₀-fraction is 85 vs. 39%, respectively, p < 0.01). Most non-SP cells are in the S or G₂/M phases (61%), which are believed to be rather radiosensitive. Thus, the difference between the SP and non-SP cell radiosensitivity can be partly explained by peculiarities of the cell cycle distribution. The NO concentration is 1.5 times higher in the SP than in the non-SP cells (p < 0.05); since it is known that NO inhibits apoptosis, being one of the mechanisms of genetic stability maintenance, that there is a higher number of the spontaneous double-strand DNA breaks in the SP cells is not surprising (p < 0.05). The above-given results to a certain extent explain the higher resistance of the SP cells to low-LET radiation in comparison with the non-SP cells. Further study of this problem may become the basis for development of tools to target SP cells and, eventually, for more effective treatment of oncological diseases.     

Antisense RNA decreases AP33 gene expression and cytoadherence by <Emphasis Type="Italic">T. vaginalis</Emphasis>

Background  

Host parasitism by Trichomonas vaginalis is complex. Adherence to vaginal epithelial cells (VECs) is mediated by surface proteins. We showed before that antisense down-regulation of expression of adhesin AP65 decreased amounts of protein, which lowered levels of T. vaginalis adherence to VECs. We now perform antisense down-regulation of expression of the ap33 gene to evaluate and confirm a role for AP33 in adherence by T. vaginalis. We also used an established transfection system for heterologous expression of AP33 in T. foetus as an additional confirmatory approach.     

Bystander normal human fibroblasts reduce damage response in radiation targeted cancer cells through intercellular ROS level modulation

The radiation-induced bystander effect is a well-established phenomenon which results in damage in non-irradiated cells in response to signaling from irradiated cells. Since communication between irradiated and bystander cells could be reciprocal, we examined the mutual bystander response between irradiated cells and co-cultured with them non-irradiated recipients. Using a transwell culture system, irradiated human melanoma (Me45) cells were co-cultured with non-irradiated Me45 cells or normal human dermal fibroblasts (NHDF) and vice versa. The frequency of micronuclei and of apoptosis, ROS level, and mitochondrial membrane potential were used as the endpoints. Irradiated Me45 and NHDF cells induced conventional bystander effects detected as modest increases of the frequency of micronuclei and apoptosis in both recipient neighbors; the increase of apoptosis was especially high in NHDF cells co-cultured with irradiated Me45 cells. However, the frequencies of micronuclei and apoptosis in irradiated Me45 cells co-cultured with NHDF cells were significantly reduced in comparison with those cultured alone. This protective effect was not observed when irradiated melanomas were co-cultured with non-irradiated cells of the same line, or when irradiated NHDF fibroblasts were co-cultured with bystander melanomas. The increase of micronuclei and apoptosis in irradiated Me45 cells was paralleled by an increase in the level of intracellular reactive oxygen species (ROS), which was reduced significantly when they were co-cultured for 24h with NHDF cells. A small but significant elevation of ROS level in NHDF cells shortly after irradiation was also reduced by co-culture with non-irradiated NHDF cells. We propose that in response to signals from irradiated cells, non-irradiated NHDF cells trigger rescue signals, whose nature remains to be elucidated, which modify the redox status in irradiated cells. This inverse bystander effect may potentially have implications in clinical radiotherapy.     

Effect of synthetic tripeptides on hemopoietic stem cells in norm and after gamma-irradiation

Our work was aimed at researching into the influence of dipeptide (gamma-dGlu-dTrp) "Timodepressin" and this dipeptide-based tripeptides on the colony-forming ability of the irradiated in vitro bone marrow and hemopoietic stem cells of the normal organism. Also studied was the effect of various doses (1-1000 microg/kg) of one oftripeptides (dAla-gammadGlu-dTrp) on the output of exogenous splenic colonies in the case of its introduction 48 hours before irradiation. It is shown that the mode of influence of the preparations produced on the basis ofdipeptides dGlu-dTrp and gamma-dGlu-dTrp on the initial stages ofa hemopoiesis in the normal and irradiated organism depends on the nature of the additional amino-acid residue and its optical orientation.     

Sensitivity of SP cell line of melanoma B16 to low- and high-ionizing radiation

Cancer stem cells (CSC) found in multiple tumor types and cancer cell lines were shown to be more resistant to low-LET radiation in comparison to other cancer cells. Therefore, CSC are supposed to determine the long-term effect of cancer therapy. Research into the CSC sensitivity to high-LET radiation is of great interest because of the advances in hadron therapy. The aim of this investigation is to compare CSC and other cancer cell sensitivity to the low- (60Co gamma-rays) and high-LET (neutron) radiation. To identify CSC, we used the low cytometry-based side population (SP) technique based on the CSC capacity to produce the efflux of the vital dye Hoechst 33342. SP and non SP cells were sorted and exposed to gamma and neutron radiation at doses of 1-10 Gy and 0.1-4.7 Gy, correspondingly. We applied the colony-formation test to examine the SP and non SP survival rate after irradiation. It was shown that the sensitivity of SP to gamma-irradiation was lower than that of other cells: D0 average values (+/- SE) made up 2.3 +/- 0.3 Gy and 1.4 +/- 0.2 Gy, correspondingly (p = 0.047). The survival rate of SP and non SP did not differ after neutron irradiation. The values of relative biological effectiveness of neutron radiation relative to gamma-radiation at the D10 level were 2.6 for SP and 2.1 for other cells. The obtained results justify for the first time a high efficiency of application of neutrons in radiotherapy from the point of view of CSC elimination.     

Morphometric analysis and taxonomic revision of the Vriesea paraibica complex (Bromeliaceae)

The species related to Vriesea paraibica (Bromeliaceae, Tillandsioideae) have controversial taxonomic limits. For several decades, this group has been identified in herbarium collections as V. × morreniana, an artificial hybrid that does not grow in natural habitats. The aim of this study was to assess the morphological variation in the V. paraibica complex through morphometric analyses of natural populations. Two sets of analyses were performed: the first involved six natural populations (G1) and the second was carried out on taxa that emerged from the first analysis, but using material from herbarium collections (G2). Univariate ANOVA was used, as well as discriminant analysis of 16 morphometric variables in G1 and 18 in G2. The results of the analyses of the two groups were similar and led to the selection of diagnostic traits of four species. Lengths of the lower and median floral bracts were significant for the separation of red and yellow floral bracts. Vriesea paraibica and V. interrogatoria have red bracts; these two species are differentiated by the widths of the lower and median portions of the inflorescence and by scape length. These structures are larger in the former and smaller in the latter. Of the species with yellow floral bracts, V. eltoniana is distinguished by longer leaf blades and scapes and V. flava is characterized by its shorter sepal lengths. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 163–181.