Segmentation des IRM cérébrales par une variante bootstrapée du HMRF-EM : étude préliminaire sur fantômes

This paper deals with global statistical unsupervised magnetic resonance image (MRI) segmentation based on a Markovian model combined with the family of mixture identification algorithms EM (Hidden Markov Random Field [HMRF-EM]) and using the Bootstrap sampling, which allows a greater respect to the data independence assumption and a reduction of algorithmic complexity. This leads not only to a flexibility in the control of running time but also an improvement in the classification quality relatively to the performance shown by an earlier version of the bootstrapped HMRF-EM.     

Synthetic transformations of higher terpenoids. XXVI. 16-acetylaminomethyllabdanoids and their cytotoxicity

Coupling of methyl 16-aminomethyllambertianate with N-Boc-protected ω-amino acids resulted in 16-(N-Boc-aminononan)- and 16-(N-Boc-aminoundecan)amidomethyllabdanoids. Interaction of methyl aminomethyllambertianate with bicyclo[2.2.1]hept-5-en-2,3-dicarboxylic acid anhydride led to the amide of bicyclo[2.2.1]heptan-1,2-dicarboxylic acid with a labdanoid substituent. Reaction of methyl 16-aminomethyllambertianate with chloroacetyl chloride resulted in methyl 16-(chloroacetylaminomethyl)lambertianate; coupling of the latter with methyl esters of amino acids gave the corresponding amides of methyl lambertianate. The compounds obtained were more cytotoxic toward CEM-13, MT-4, and U-937 tumor cell lines as compared with lambertianic acid; the dose inhibiting tumor cell viability by 50% (CCID₅₀) of the more active compounds was 3.9–9.9 μM.     

Dynamics of seasonal plant growth in halophytic meadows taking into account the temperature factor and soil salinity level

A mathematical model has been constructed to describe the growth dynamics of various plant communities of halophytic meadows depending on the temperature factor and degree of soil salinity. Field investigation of the yields of halophytic meadow plant communities were performed in the coastal area of Kurinka Lake in the Altaiskii district of the Republic of Khakasia in 2004 and 2006. The results of field investigations and model studies show that there is a correlation between plant growth and air temperature for plant communities growing on soils with the lowest and medium salinity levels. It was proven in model studies that for the plant communities that grow on highly saline (3.58%) soils, not only air temperature but also the salinity level of the soil should be taken into account.     

The arsenolysis reaction in the biotechnological synthesis of ribavirin. The in vitro and in vivo inhibition of influenza A virus replication with a combination of ribavirin and ozeltamivir

The biotechnological method of synthesis of the antiviral drug ribavirin based on the transglycosylation reaction was improved due to the addition of catalytic amounts of sodium arsenate. This approach allows us to hydrolyze the excess natural nucleoside guanosine, a ribose donor, and, hence, made the composition of the reaction mixture less complicated, thus facilitating the process of ribavirin isolation. It was shown that in cell cultures the combination of ribavirin and oseltamivir carboxylate inhibited the replication of the influenza A virus more effectively than each of them alone. Similar results were obtained in experiments on laboratory animals (mouse Balb/c) infected with the influenza A virus H3N2/Aichi/68 strain.     

<Emphasis Type="Italic">Ochrobactrum</Emphasis> sp. MPV1 from a dump of roasted pyrites can be exploited as bacterial catalyst for the biogenesis of selenium and tellurium nanoparticles

Background

Bacteria have developed different mechanisms for the transformation of metalloid oxyanions to non-toxic chemical forms. A number of bacterial isolates so far obtained in axenic culture has shown the ability to bioreduce selenite and tellurite to the elemental state in different conditions along with the formation of nanoparticles—both inside and outside the cells—characterized by a variety of morphological features. This reductive process can be considered of major importance for two reasons: firstly, toxic and soluble (i.e. bioavailable) compounds such as selenite and tellurite are converted to a less toxic chemical forms (i.e. zero valent state); secondly, chalcogen nanoparticles have attracted great interest due to their photoelectric and semiconducting properties. In addition, their exploitation as antimicrobial agents is currently becoming an area of intensive research in medical sciences.

Results

In the present study, the bacterial strain Ochrobactrum sp. MPV1, isolated from a dump of roasted arsenopyrites as residues of a formerly sulfuric acid production near Scarlino (Tuscany, Italy) was analyzed for its capability of efficaciously bioreducing the chalcogen oxyanions selenite (SeO₃ ^2?) and tellurite (TeO₃ ^2?) to their respective elemental forms (Se⁰ and Te⁰) in aerobic conditions, with generation of Se- and Te-nanoparticles (Se- and TeNPs). The isolate could bioconvert 2 mM SeO₃ ^2? and 0.5 mM TeO₃ ^2? to the corresponding Se⁰ and Te⁰ in 48 and 120 h, respectively. The intracellular accumulation of nanomaterials was demonstrated through electron microscopy. Moreover, several analyses were performed to shed light on the mechanisms involved in SeO₃ ^2? and TeO₃ ^2? bioreduction to their elemental states. Results obtained suggested that these oxyanions are bioconverted through two different mechanisms in Ochrobactrum sp. MPV1. Glutathione (GSH) seemed to play a key role in SeO₃ ^2? bioreduction, while TeO₃ ^2? bioconversion could be ascribed to the catalytic activity of intracellular NADH-dependent oxidoreductases. The organic coating surrounding biogenic Se- and TeNPs was also characterized through Fourier-transform infrared spectroscopy. This analysis revealed interesting differences among the NPs produced by Ochrobactrum sp. MPV1 and suggested a possible different role of phospholipids and proteins in both biosynthesis and stabilization of such chalcogen-NPs.

Conclusions

In conclusion, Ochrobactrum sp. MPV1 has demonstrated to be an ideal candidate for the bioconversion of toxic oxyanions such as selenite and tellurite to their respective elemental forms, producing intracellular Se- and TeNPs possibly exploitable in biomedical and industrial applications.

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