Siderophores and hemolysins in iron aquisition by Acinetobacter genus

In 60 strains of Acinetobacter genus isolated from clinical material belonging to species A. baumannii, A. haemolyticus, A. junii and A. lwoffii a hydroxamate and phenol-catechol class siderophores was identified by chemical and biological testes. A correlation between siderophores production and growth intensity, species affiliation and origin of strains was found.     

Synthesis and biological activity of N(alpha)-[4-[N-[(3,4-dihydro-2-methyl-4-oxo-6-quinazolinyl)methyl]-N-propargylamino]phenylacetyl]-L-glutamic acid

2-Deamino-2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI 198583) is a potent inhibitor of thymidylate synthase. Its analogue, N(alpha)-[4-[N-[(3,4-dihydro-2-methyl-4-oxo-6-quinazolinyl)methyl]-N-propargylamino]phenylacetyl]-L-glutamic acid, containing p-aminophenylacetic acid residue substituting p-aminobenzoic acid residue, was synthesized. The new analogue exhibited a moderately potent thymidylate synthase inhibition, of linear mixed type vs. the cofactor, N(5,10)-methylenetetrahydrofolate. The Ki value of 0.34 microM, determined with a purified recombinant rat hepatoma enzyme, was about 30-fold higher than that reported for inhibition of thymidylate synthase from mouse leukemia L1210 cells by ICI 198583 (Hughes et al., 1990, J. Med. Chem. 33, 3060). Growth of mouse leukemia L5178Y cells was inhibited by the analogue (IC50 = 1.26 mM) 180-fold weaker than by ICI 198583 (IC50 = 6.9 microM).     

Evaluation of mouse preimplantation embryos exposed to oxidative stress cultured with insulin-like growth factor I and II, epidermal growth factor, insulin, transferrin and selenium

Blastocyst culture requires strictly defined culture media to sustain its viability and quality. Although blastocyst media are commercially available, they do not meet all the needs and research focused on blastocyst-promoting agents is on the way. The aims of the study were to evaluate the significance of insulin-like growth factors I (IGF-I) and II (IGF-II); epidermal growth factor (EGF) and a mixture of insulin, transferrin and selenium (ITS) on the development of embryos exposed to oxidative stress. C3B6F1 mice were stimulated with 5 IU of pregnant mare serum gonadotropin following by administration of 5 IU of equine chorionic gonadotropin and mating with DBA males. The mice were killed 40 h after eCG injection by cervical dislocation and then the 2 cell embryos were flushed out from the fallopian tubes. To evaluate whether the growth factors may compensate the unfavorable--oxidative milieu created by hydrogen peroxide (H2O2), the embryos were transferred to 1/ control medium, 2/ control medium+0.1 mM (H2O2) or 3/ control medium+H2O2 enriched with 10(-7) g/ml of IGF-I, IGF-II, EGF or a mixture of insulin (5x10(-6) g/ml), transferrin (5 x10(-6) g/ml) and selenium (5x10(-9) g/ml; ITS). Embryos were evaluated 96-144 hours following eCG injection. In the study the dynamics of embryo development and blastocyst cell numbers (including inner cell mass) were assessed. The morphological evaluation comprised viability and apoptosis (TUNEL). In oxidative stress setting, IGF-I, IGF-II, EGF and ITS minimized the negative influence of H2O2, and embryos developed faster than in control conditions. Blastocysts cultured with hydrogen peroxide and growth factors or ITS displayed normal morphology and had more cells--also within the inner cell mass--than those treated only with H2O2. The positive TUNEL reactions were sporadically observed in embryos cultured with hydrogen peroxide supplemented with growth factors. IGF-I, IGF-II, EGF and ITS have a positive effect on pre-implantation embryo development in detrimental culture conditions of oxidative stress.     

Statistical methods for microarray assays

The paper shortly reviews statistical methods used in the area of DNA microarray studies. All stages of the experiment are taken into account: planning, data collection, data preprocessing, analysis and validation. Among the methods of data analysis, the algorithms for estimating differential expression, multivariate approaches, clustering methods, as well as classification and discrimination are reviewed. The need is stressed for routine statistical data processing protocols and for the search of links of microarray data analysis with quantitative genetic models.     

Molecular dynamics simulations of the first steps of the reaction catalyzed by HIV-1 protease

The mechanism of the first steps of the reaction catalyzed by HIV-1 protease was studied through molecular dynamics simulations. The potential energy surface in the active site was generated using the approximate valence bond method. The approximate valence bond (AVB) method was parameterized based on density functional calculations. The surrounding protein and explicit water environment was modeled with conventional, classical force field. The calculations were performed based on HIV-1 protease complexed with the MVT-101 inhibitor that was modified to a model substrate. The protonation state of the catalytic aspartates was determined theoretically. Possible reaction mechanisms involving the lytic water molecule are accounted for in this study. The modeled steps include the dissociation of the lytic water molecule and proton transfer onto Asp-125, the nucleophilic attack followed by a proton transfer onto peptide nitrogen. The simulations show that in the active site most preferable energetically are structures consisting of ionized or polarized molecular fragments that are not accounted for in conventional molecular dynamics. The mobility of the lytic water molecule, the dynamics of the hydrogen bond network, and the conformation of the aspartates in the active center were analyzed.     

Adhesion of human T lymphocytes and granulocytes to endothelial cells stimulated by cell-surface antigens of Bacteroides thetaiotaomicron

The aim of this study was to assay the degree of human T lymphocyte and granulocyte adhesion to the vascular endothelial cells stimulated by Bacteroides thetaiotaomicron lipopolysaccharides, components of LPS and capsular polysaccharide. HMEC-1 cells were activated with bacterial preparations in concentration 10 micrograms/ml for 4 and 24 hours. T lymphocytes and granulocytes were isolated from peripheral blood of healthy blood donors. Thereafter, the adhesion tests of granulocytes and adhesion tests of non-activated and activated with PMA (in concentration 10 ng/ml) T lymphocytes to the resting and stimulated vascular endothelium were performed. The number of viable cells, which adhered to the endothelium, was determined using inverted microscope (magnification 200x). The results were presented as the number of viable cells adhering to 1 mm2 of the endothelial cell culture. The obtained results indicate that granulocytes and T lymphocytes (resting and activated with PMA) adhere to the endothelial cells stimulated by B. thetaiotaomicron cell-surface antigens. B. thetaiotaomicron lipopolysaccharides and capsular polysaccharide are weaker stimulants of human leukocyte adhesion to the HMEC-1 cells than E. coli O55:B5 LPS.     

Accumulation of selected heavy metals by different genotypes of Salix

The aim of this study was to assess the accumulation of seven heavy metals (lead, cadmium, copper, zinc, chrome, nickel and cobalt). The investigations were conducted on twelve genotypes of willows which grow in the Potasze Forest Division Salicarium. The analysis facilitated quantification of concentrations of selected metals in plants and their comparison in relation to sorption ability of each willow genotype. Simultaneously the studies allowed us to demonstrate essential differentiation of metal size sorption within the species Salix purpurea and in relation to the other genotypes. The results confirm the complexity of factors influencing the efficiency of heavy metal accumulation by willow; they indicate increasing ion absorption in the case of some metals, while the accumulation of other heavy metal ions was limited.     

Early steps in plastid evolution: current ideas and controversies

Some nuclear‐encoded proteins are imported into higher plant plastids via the endomembrane (EM) system. Compared with multi‐protein Toc and Tic translocons required for most plastid protein import, the relatively uncomplicated nature of EM trafficking led to suggestions that it was the original transport mechanism for nuclear‐encoded endosymbiont proteins, and critical for the early stages of plastid evolution. Its apparent simplicity disappears, however, when EM transport is considered in light of selective constraints likely encountered during the conversion of stable endosymbionts into fully integrated organelles. From this perspective it is more parsimonious to presume the early evolution of post‐translational protein import via simpler, ancestral forms of modern Toc and Tic plastid translocons, with EM trafficking arising later to accommodate glycosylation and/or protein targeting to multiple cellular locations. This hypothesis is supported by both empirical and comparative data, and is consistent with the relative paucity of EM‐based transport to modern primary plastids.     

Delayed reconstruction of the upper digestive tract in a patient following total pharyngolaryngectomy with resection of the cervical oesophagus

Carcinoma of the hypopharynx is an uncommon disease, with an annual incidence of approximately 1 in 100,000. Post-cricoid carcinoma is more common in women and is not usually associated with tobacco and alcohol abuse. Reconstruction of large pharyngeal defects following surgery for squamous cell carcinoma is complex and often requires microvascular free tissue transfer to achieve the best oncological and functional outcomes. The most common complications of such procedures include fistulas and strictures of the neopharynx. Here, we describe a case of a female patient admitted to the Head and Neck Department at our hospital to undergo delayed reconstruction following pharyngolaryngectomy and removal of the cervical oesophagus. Several complications occurred during post-operative care, including stricture and skin dehiscence. At present, the patient is able to swallow saliva and is currently being prepared to return to a normal diet.