Mechanism of Resistance to an Antitubercular 2-Thiopyridine Derivative That Is Also Active against Burkholderia cenocepacia

The discovery of new compounds that are able to inhibit the growth of Burkholderia cenocepacia is of primary importance for cystic fibrosis patients. Here, the mechanism of resistance to a new pyridine derivative already shown to be effective against Mycobacterium tuberculosis and to have good activity toward B. cenocepacia was investigated. Increased expression of a resistance-nodulation-cell division (RND) efflux system was detected in the resistant mutants, thus confirming their important roles in B. cenocepacia antibiotic resistance.     

Differential scanning calorimetric study of antibiotic distamycin A binding with chromatin within isolated rat liver nuclei

Context: Natural oligopeptide antibiotic distamycin A (Dst) biosynthesized by Streptomyces distallicus is traditionally used in medical practice as an anti-inflammatory and antitumour drug.

Objective: Dst was investigated for its effect on the structural components of native chromatin directly within isolated rat liver nuclei in the presence of physiologically significant cations (magnesium or spermine and spermidine).

Materials and methods: Differential scanning calorimetry (DSC) was used to study the Dst action at molar ratio Dst/DNA?=?0.1 and 0.15?mM Dst on the melting profile of nuclei suspension in different conditions.

Results: Results showed that the thermodynamic parameters of control nuclei in the presence of polyamines or Mg^2+?were different. The incubation of nuclei with Dst raised transition temperatures of relaxed (peak II) and topologically constrained DNA (peak III) by 6–8?°C and decreased by 2–4?°C that of core-histones (peak I). The total excess transition enthalpy (ΔH_exc) in buffer with polyamines (24.7?kJ/mol DNA nucleotides) increased by1.5 times versus control but in buffer with Mg²⁺, the value of ΔH_exc (35.8?kJ/mol DNA nucleotides) remained unchanged.

Conclusions: The association of Dst with chromatin in the nucleus weakens histone-DNA contacts and causes additional strengthening of interaction between two complementary DNA chains. Our results contribute towards validation of DSC to test drug ability to modulate chromatin structure in the physiological environment and to clarify the mechanism of these modulations.     

Genetic stability of Brucella abortus S19 and RB51 vaccine strains by multiple locus variable number tandem repeat analysis (MLVA16)

The aims of the present study were (i) to assess the in vitro genetic stability of S19 and RB51 Brucella abortus vaccines strains and (ii) to evaluate the ability of multiple-locus variable-number tandem repeat (VNTR) analysis (MLVA) as a tool to be used in the quality control of live vaccines against brucellosis. Sixty-three batches of commercial S19 (n = 53) and RB51 (n = 10) vaccines, produced between 2006 and 2009, were used in this study. S19 and RB51 vaccines were obtained from, respectively, seven and two different manufacturers. Ten in vitro serial passages were performed on reference strains and on selected batches of commercial vaccines. All batches, reference strains and strains of serial passages were typed by the MLVA16. The results demonstrated that B. abortus S19 and RB51 vaccine strains are genetically stable and very homogeneous in their respective groups. Anyway, batches of S19 from one manufacturer and batches of RB51 from another presented genotypes distincts from the reference vaccine strains. In both cases, differences were found on locus Bruce07, which had addition of one repeat unit in the case of S19 batches and the deletion of one repeat unit in the case of RB51 batches. In summary, MLVA16 proved to be a molecular tool capable of discriminating small genomic variations and should be included in in vitro official tests.     

Nanocrystalline TiO2 doped by small amount of pre-synthesized colloidal CdS nanoparticles for photocatalytic degradation of 1,2,4-trichlorobenzene

The chemical stability and hydrophobic nature of chloroarenes make them a persistent environmental hazard. Modeling of 1,2,4-trichlorobenzene (1,2,4-TCB) degradation in alcohol-water solution under UV irradiation was carried out with the aim of probing how the 1,2,4-TCB might behave in the environment. The photocatalytic activity of both bare TiO₂ and TiO₂ doped by colloidal CdS nanoparticles synthesized by the sol-gel method has been investigated in the processes of 1,2,4-TCB photodegradation in the aqueous protic solvent. Non-sensitized TiO₂ cannot be regarded as catalyst for the 1,2,4-TCB photodecomposition. On the contrary, the CdS/TiO₂ composite accelerated the 1,2,4-TCB photodegradation process. The concentration of CdS/TiO₂ was shown to effect on the 1,2,4-TCB photolysis mechanisms, which resulted in the quantitative ratios of the 1,2,4-TCB photolysis products.     

Cysteine protease mcII-Pa executes programmed cell death during plant embryogenesis

Programmed cell death (PCD) is indispensable for eukaryotic development. In animals, PCD is executed by the caspase family of cysteine proteases. Plants do not have close homologues of caspases but possess a phylogenetically distant family of cysteine proteases named metacaspases. The cellular function of metacaspases in PCD is unknown. Here we show that during plant embryogenesis, metacaspase mcII-Pa translocates from the cytoplasm to nuclei in terminally differentiated cells that are destined for elimination, where it colocalizes with the nuclear pore complex and chromatin, causing nuclear envelope disassembly and DNA fragmentation. The cell-death function of mcII-Pa relies on its cysteine-dependent arginine-specific proteolytic activity. Accordingly, mutation of catalytic cysteine abrogates the proteolytic activity of mcII-Pa and blocks nuclear degradation. These results establish metacaspase as an executioner of PCD during embryo patterning and provide a functional link between PCD and embryogenesis in plants. Although mcII-Pa and metazoan caspases have different substrate specificity, they serve a common function during development, demonstrating the evolutionary parallelism of PCD pathways in plants and animals.     

A novel IVS2 -2A>T splicing mutation in the GH-1 gene in familial isolated growth hormone deficiency type II in the spectrum of other splicing mutations in the Russian population

Isolated GH deficiency (IGHD) is characterized by genetic heterogeneity, both in familial and sporadic cases. To determine if this statement can be applied to the Russian population, we performed screening for mutations in the GH-1 gene in children living in Russia with IGHD. Twenty-eight children from 26 families with total IGHD were studied. DNA fragments, covering each of four (2-5) exons of GH-1 were amplified using PCR. Single-strand conformation polymorphism analysis followed by direct DNA sequencing identified five heterozygous mutations of splicing in intron 2, intron 3, and exon 4 of GH-1; three of them were not previously reported. We concentrated here on dominant-negative mutations causing IGHD type II, which were as follows: 1) A>T transversion of the second base of the 3'-acceptor splice site of intron 2 (IVS2 -2A>T); 2) T>C transition of the second base of the 5'-donor splice site of intron 3 (IVS3 +2T>C); 3) G>A transition of the first base of the 5'-donor splice site of intron 3 (IVS3 +1G>A). Our data indicate allelic heterogeneity of IGHD type II (IGHD II). However, all mutations in Russian IGHD II patients affect splicing, a striking difference from the mutation spectrum of other IGHD forms. The IVS2 -2A>T mutation is the first identified mutation in intron 2 of GH-1. The 5'-donor splice site of intron 3 of GH-1 is a mutational hot spot, and the IVS3 +1G>A mutation can be considered to be a common molecular defect in IGHD II in Russian patients.