Mitochondrial localization as a determinant of capacitative Ca2+ entry in HeLa cells

Whether different subsets of mitochondria play distinct roles in shaping intracellular Ca2+ signals is presently unresolved. Here, we determine the role of mitochondria located beneath the plasma membrane in controlling (a) Ca2+ release from the endoplasmic reticulum (ER) and (b) capacitative Ca2+ entry. By over-expression of the dynactin subunit dynamitin, and consequent inhibition of the fission factor, dynamin-related protein (Drp-1), mitochondria were relocalised from the plasma membrane towards the nuclear periphery in HeLa cells. The impact of these changes on free calcium concentration in the cytosol ([Ca2+]c), mitochondria ([Ca2+]m) and ER ([Ca2+]ER) was then monitored with specifically-targeted aequorins. Whilst dynamitin over-expression increased the number of close contacts between the ER and mitochondria by >2.5-fold, assessed using organelle-targeted GFP variants, histamine-induced changes in organellar [Ca2+] were unaffected. By contrast, Ca2+ influx elicited significantly smaller increases in [Ca2+]c and [Ca2+]m in dynamitin-expressing than in control cells. These data suggest that the strategic localisation of a subset of mitochondria beneath the plasma membrane is required for normal Ca2+ influx, but that the transfer of Ca2+ ions between the ER and mitochondria is relatively insensitive to gross changes in the spatial relationship between these two organelles.     

Novel ruthenium complex K2[Ru(dmgly)Cl4].2H2O is toxic to C6 astrocytoma cell line, but not to primary rat astrocytes

A novel class of ruthenium (III) complexes of formulas K[Ru(sar)2Cl2].12H2O and K2[Ru(dmgly)Cl4].2H2O, containing bidentate chelates N-methylglycine (sarcosine, sar) or N,N-dimethylglycine (dmgly) and additional chloro ligands were synthesized. The complexes have been obtained by direct reaction of ruthenium(III) chloride with corresponding bidentate ligand followed by addition of base (KOH). These new complexes were characterized by elemental analysis, IR and electronic absorption spectroscopy. As astrocytomas, the most common of all brain tumors, are still very difficult to treat, we examined the influence of newly synthesized ruthenium-based complexes, as well as the earlier synthesized analogue platinum(IV) complexes [Pt(dmgly)2Cl2], [Pt(sar)2Br2] and [Pt(dmgly)2Br2], on rat astrocytoma C6 cells in vitro. Among these complexes only K2[Ru(dmgly)Cl4].2H2O and [Pt(dmgly)2Br2] markedly inhibited the viability of non-confluent C6 cells. Furthermore, only complex K2[Ru(dmgly)Cl4].2H2O was able to reduce viability in confluent C6 cultures. Importantly, this complex was not toxic to primary rat astrocytes or macrophages. Having in mind that appropriate chemotherapy should be effective against tumor cells without harming normal tissues, complex K2[Ru(dmgly)Cl4].2H2O could be a promising agent for developing therapeutics against astrocytomas.     

Multivariate exploratory tools for microarray data analysis

The ultimate success of microarray technology in basic and applied biological sciences depends critically on the development of statistical methods for gene expression data analysis. The most widely used tests for differential expression of genes are essentially univariate. Such tests disregard the multidimensional structure of microarray data. Multivariate methods are needed to utilize the information hidden in gene interactions and hence to provide more powerful and biologically meaningful methods for finding subsets of differentially expressed genes. The objective of this paper is to develop methods of multidimensional search for biologically significant genes, considering expression signals as mutually dependent random variables. To attain these ends, we consider the utility of a pertinent distance between random vectors and its empirical counterpart constructed from gene expression data. The distance furnishes exploratory procedures aimed at finding a target subset of differentially expressed genes. To determine the size of the target subset, we resort to successive elimination of smaller subsets resulting from each step of a random search algorithm based on maximization of the proposed distance. Different stopping rules associated with this procedure are evaluated. The usefulness of the proposed approach is illustrated with an application to the analysis of two sets of gene expression data.     

Bacteremic meningitis is associated with inferior outcome in comparison to community acquired meningitis without bacteremia

Meningitis associated with bacteremia is rare. Bacteremic form of meningitis occurred in 28 of 201 cases of community acquired meningitis (14%) in Slovakia within last 17 years. Bacteremic meningitis was associated with diabetes (21.4% vs. 7.5%, p=0.02) and with higher treatment failures (32.1% vs. 9.5%, p=0.01) and higher mortality (25% vs. 12.4%, NS). In univariate analysis comparing 28 cases of bacteremic community acquired bacterial meningitis (BCBM) to all CBM, no significant risk factor concerning underlying disease (cancer, ENT infection, alcohol abuses, trauma, splenectomy, etc.) or etiology was observed apart of diabetes mellitus, which was more common among bacteremic meningitis (21.4% vs. 7.5%, p=0.02). Mortality (25% vs. 12.4%, NS) insignificantly but therapy failure (32.1% vs. 9.5%, p=0.01) was significantly more frequently observed among meningitis with bacteremia. N. meningitis was the commonest causative agent (8 of 28 cases) followed by Str. pneumoniae (6), gram-negative bacteria (6), S. aureus (4) and H. influenzae (2).     

NRF IRES activity is mediated by RNA binding protein JKTBP1 and a 14-nt RNA element

The mRNA of human NF-kappaB repressing factor (NRF) contains a long 5'-untranslated region (UTR) that directs ribosomes to the downstream start codon by a cap-independent mechanism. Comparison of the nucleotide (nt) sequences of human and mouse NRF mRNAs reveals a high degree of identity throughout a fragment of 150 nt proximal to the start codon. Here, we show that this region constitutes a minimal internal ribosome entry segment (IRES) module. Enzymatic RNA structure analysis reveals a secondary structure model of the NRF IRES module. Point mutation analysis of the module determines a short, 14-nt RNA element (nt 640-653) as a mediator of IRES function. Purification of IRES binding cellular proteins and subsequent ESI/MS/MS sequence analysis led to identification of the RNA-binding protein, JKTBP1. EMSA experiments show that JKTBP1 binds upstream to the 14-nt RNA element in the NRF IRES module (nt 579-639). Over-expression of JKTBP1 significantly enhances activity of the NRF IRES module in dicistronic constructs. Moreover, siRNA experiments demonstrate that down-regulation of endogenous JKTBP1 decreases NRF IRES activity and the level of endogenous NRF protein. The data of this study show that JKTBP1 and the 14-nt element act independently to mediate NRF IRES activity.     

Impedance spectroscopy of bilayer lipid membranes self-assembled on agar support - interaction with HDL

The electrical properties of the supported lipid bilayer membrane (s-BLM) of egg phosphatidylcholine (PC) self-assembled on agar surface were examined. To characterize the insulating properties of s-BLMs, electrochemical impedance spectroscopy (EIS) was used. The analysis of impedance spectra in terms of an equivalent circuit of agar/electrolyte and agar/s-BLM/electrolyte in the frequency range of 0.1 Hz-10 kHz was performed. The high-density lipoproteins (HDL)/s-BLM interaction in the concentration range from 20 microg/ml to 80 microg/ml of HDL was investigated. It is evident that treatment of s-BLM with HDL resulted in an increase of the lipid film resistance and a decrease of membrane capacitance.