Changes in S-type lectin localization in neuroblastoma cells (N1E115) upon differentiation

The distribution of a 14.4 kDa S-type lectin was examined in murine neuroblastoma cells, either undifferentiated or after differentiation induced by dibutyryl-cyclic adenosine monophosphate. In undifferentiated cells the immunoreactivity was detected extracellularly, associated with the plasma membrane and in bulges released into the extracellular milieu. Important modifications of the lectin localization were associated with the differentiation process that induced an increased cytosolic expression and a decreased externalization. Possible functions for the lectin expressed intracellularly in the differentiated cells are also considered.     

The enterotoxin gene (cpe) of Clostridium perfringens can be chromosomal or plasmid-borne

The location of the cpe gene, encoding the enterotoxin responsible for food poisoning in humans, has been studied in a series of enterotoxigenic Ciostridium perfringens strains by means of pulsed field gel electrophoresis of genomic DNA. The cpe gene was found at the same chromosomal locus in strains associated with food poisoning in humans and was shown to be linked to a repetitive sequence, the Hin dlll repeat, and an open reading frame, ORF3, that may be part of an insertion sequence. In contrast, when the strains originated from domesticated livestock cpe was located on a large episome where it was often close to a copy of the transposable element IS 1151. In these cases, the Hin dlll repeat was not linked to the cpe gene although this was generally preceded by ORF3.     

Functional analysis of <Emphasis Type="Italic">Plasmodium falciparum</Emphasis> subpopulations associated with artemisinin resistance in Cambodia

Background

Plasmodium falciparum malaria is one of the most widespread parasitic infections in humans and remains a leading global health concern. Malaria elimination efforts are threatened by the emergence and spread of resistance to artemisinin-based combination therapy, the first-line treatment of malaria. Promising molecular markers and pathways associated with artemisinin drug resistance have been identified, but the underlying molecular mechanisms of resistance remains unknown. The genomic data from early period of emergence of artemisinin resistance (2008–2011) was evaluated, with aim to define k13 associated genetic background in Cambodia, the country identified as epicentre of anti-malarial drug resistance, through characterization of 167 parasite isolates using a panel of 21,257 SNPs.

Results

Eight subpopulations were identified suggesting a process of acquisition of artemisinin resistance consistent with an emergence-selection-diffusion model, supported by the shifting balance theory. Identification of population specific mutations facilitated the characterization of a core set of 57 background genes associated with artemisinin resistance and associated pathways. The analysis indicates that the background of artemisinin resistance was not acquired after drug pressure, rather is the result of fixation followed by selection on the daughter subpopulations derived from the ancestral population.

Conclusions

Functional analysis of artemisinin resistance subpopulations illustrates the strong interplay between ubiquitination and cell division or differentiation in artemisinin resistant parasites. The relationship of these pathways with the P. falciparum resistant subpopulation and presence of drug resistance markers in addition to k13, highlights the major role of admixed parasite population in the diffusion of artemisinin resistant background. The diffusion of resistant genes in the Cambodian admixed population after selection resulted from mating of gametocytes of sensitive and resistant parasite populations.

     

Metagenomic approach studying the taxonomic and functional diversity of the bacterial community in a mesotrophic lake (Lac du Bourget – France)

The main goals of this work were to identify the metabolic pathways of the bacterial community in a lacustrine ecosystem and to establish links between taxonomic composition and the relative abundances of these metabolic pathways. For this purpose, we analysed a 16S rRNA gene library obtained by gene amplification together with a sequence library of both insert ends on c . 7700 fosmids. Whatever the library used, Actinobacteria was the most abundant bacterial group, followed by Proteobacteria and Bacteroidetes . Specific aquatic clades such as acI and acIV ( Actinobacteria ) or LD12 and GOBB-C201 ( Alphaproteobacteria ) were found in both libraries. From comparative analysis of metagenomic libraries, the metagenome of this lake was characterized by overrepresentation of genes involved in the degradation of xenobiotics mainly associated with Alphaproteobacteria . Actinobacteria were mainly related to metabolic pathways involved in nucleotide metabolism, cofactors, vitamins, energy, replication and repair. Betaproteobacteria appeared to be characterized by the presence of numerous genes implicated in environmental information processing (membrane transport and signal transduction) whereas glycan and carbohydrate metabolism pathways were overrepresented in Bacteroidetes . These results prompted us to propose hypotheses on the ecological role of these bacterial classes in lacustrine ecosystems.     

Affinity electrophoresis: Role of the interposition of spacers between particles and ligands in adsorption and elution processes

Anti-albumin was coupled to Sepharose 4B with interposition of spacers of different lengths. The different type of immunoadsorbents obtained were used in two ways: (i) migration of human albumin through the adsorbent in an electric field; and (ii) adsorption in a first chromatographic step and then elution in a second electrophoretic step. Without a spacer or with a short one, the association between Sepharose-anti-human albumin and albumin is partially reversible under the conditions of electrophoresis. With long spacers no dissociation of the antigen-antibody complex is obtained. The effects of the different spacers and of sterid hindrance in affinity electrophoresis and in affinity chromatography are discussed.     

Use of an immobilized human endogenous lectin for the purification of complementary ligands.

1. A galactoside-specific endogenous lectin isolated from human brain was covalently immobilized on divinylsulfone-activated agarose. This highly selective affinity adsorbent proved to be useful in purifying soluble protein ligands. 2. The maximum binding capacity of the adsorbent for complementary proteins was calculated to be 618 micrograms per g of gel (wet resin). 3. Sequential elutions using 0.1 M lactose, 0.3 M lactose and 0.5 M NaCl, and competition assays using incorporation in the presence 0.1 M lactose revealed differences in lectin-ligand interactions.     

Fine analysis of the Pneumocystis carinii f. sp. carinii genome by two-dimensional pulsed-field gel electrophoresis

Pneumocystis carinii is a general designation for a group of unusual unicellular fungal parasites responsible of pneumopathy in animal hosts. Divided into several subgroups termed the 'special forms', P. carinii is prone to an extensive karyotype variation. In previous studies, the nuclear genome of these organisms has been considered to be haploid and a set of 16 chromosomes has been assigned to P. carinii f. sp. carinii, a special form known to infect rats. We report the analysis of the genome of an isolate representative of the karyotype 1 of this special form, using two-dimensional pulsed-field gel electrophoresis procedures. The 'karyotype and restriction display' (KARD) fingerprints indicated the presence of 17 different chromosomes. The haploid genome size was estimated to be 8.4 Mbp. Some homologous chromosomes were distinguished on the basis of a single restriction fragment length polymorphism, which raises the possibility of a diploid nucleus. A restriction map of the chromosome 15, characterized by two homologues with a size difference of 7 kb, was constructed. Hybridization data indicated that insertion/deletion events may have occurred within subtelomeric regions which carry genes encoding the major surface glycoprotein (MSG) of Pneumocystis.     

Spraguea lophii (Microsporidia) parasite of the teleost fish,Lophius piscatorius from Tunisian coasts: Evidence for an extensive chromosome length polymorphism

A microsporidian of the genus Spraguea was found parasitizing the nervous tissues of Lophius piscatorius collected from various localities in the Mediterranean coastal areas of Tunisia. The tissue localization, the infection focus aspect and sporal dimorphism are characteristics of Spraguea lophii species. Molecular data based on partial sequence of SSUrRNA encoding gene shows few nucleotide polymorphisms, compared to all described Spraguea isolates. Molecular karyotype obtained on pulsed field gel electrophoresis (1D-PFGE) shows a profile with 14 stained bands in the range of 230–880 kbp and a genome size estimated to 6.700 kbp. The rare cutter endonuclease MluI KARD 2-D-PFGE fingerprint shows an extensive chromosome length polymorphism, but the number of chromosome is unchanged and consists of 15 different molecules. The extensive chromosome length polymorphism is associated to a reduced number of genetic events.     

The role of sialic acid in the determination of survival of rabbit erythrocytes in the circulation

Evidence is presented to indicate a generalized role for the terminal sialic acid residues of circulating erythrocytes of rabbit. Neuraminidase is shown to remove only sialic acid from these erythrocytes. Neuraminidase-treated and intact rabbit erythrocytes have similar in vitro properties, except those of cellular charge and cellular adhesion in their sera. These properties include similar shape, osmotic fragility curve, autohemolysis at 37°, K⁺ retention and pyruvate kinase activity. The D-glucose 6-phosphate dehydrogenase and the cholinesterase activities are higher on the neuraminidase-treated erythrocytes than on the intact ones. After injection into rabbits, the sialic acid-less erythrocytes tested, were promptly removed from the circulation; intact erythrocytes, previously incubated under the same conditions but without neuraminidase, were removed from the circulation after a significantly longer period.