Risk of vertical transmission of hepatitis B virus in Tunisia

The risk of vertical transmission of hepatitis B virus (HBV) varies with type of viral endemicity, degree of maternal infection and genomic characteristics of the virus. The aim of this study is to estimate this risk in Tunisia using serological and molecular methods to evaluate HBV replication, to determine viral genotypes and to detect presence of occult hepatitis in 2709 pregnant women. Serological markers were detected by ELISA methods, Genotype was determined by PCR-RFLP and occult hepatitis by nested-PCR. Four percent of women were positive for HBsAg; only 3% of them were also positive for HBeAg. Viral replication, over than 10(3) copies/ml, was detected in 61% of positive HBsAg patients. Three viral genotypes were detected: D (95%), B (3%) and A (3%). Occult hepatitis was detected in 4% of sera with "anti-HBc isolated" profile. In conclusion, the risk of vertical transmission of HBV exists in Tunisia. It increases by frequency of precore mutants, predominance of the genotype previously associated with high levels of replication and possibility of occult hepatitis B. These results show the importance of screening by serological HBV markers systematically during pregnancy with evaluation of viral replication in order to prevent vertical risk by efficient tools.     

The epidemiology underlying age‐related avian malaria infection in a long‐lived host: the mute swan Cygnus olor

Quantifying the factors that predict parasite outbreak and persistence is a major challenge for both applied and fundamental biology. Key to understanding parasite prevalence and disease outbreaks is determining at what age individuals show signs of infection, and whether or not they recover. Age‐dependent patterns of the infection of a host population by parasites can indicate among‐individual heterogeneities in their susceptibility to, or rate of recovery from, parasite infections. Here, we present a cross‐sectional study of avian malaria in a long‐lived bird species, the mute swan Cygnus olor, examining age‐related patterns of parasite prevalence and modelling patterns of infection and recovery. One‐hundred and fifteen swans, ranging from one to nineteen years old, were screened for infection with Plasmodium, Haemoproteus and Leucocytozoon parasites. Infections with three cytochrome‐b lineages of Haemoproteus were found (pooled prevalence 67%), namely WW1 (26%), which is common in passerine birds, and two new lineages closely related to WW1: MUTSW1 (25%) and MUTSW2 (16%). We found evidence for age‐related infection in one lineage, MUTSW1. Catalytic models examining patterns of infection and recovery in the population suggested that infections in this population were not life‐long – recovery of individuals was included in the best fitting models. These findings support the results of recent studies that suggest hosts can clear infections, although patterns of infection‐related mortality in older birds remain to be studied in more detail.     

Quantifying bacterial evolution in the wild: A birthday problem for Campylobacter lineages

Measuring molecular evolution in bacteria typically requires estimation of the rate at which nucleotide changes accumulate in strains sampled at different times that share a common ancestor. This approach has been useful for dating ecological and evolutionary events that coincide with the emergence of important lineages, such as outbreak strains and obligate human pathogens. However, in multi-host (niche) transmission scenarios, where the pathogen is essentially an opportunistic environmental organism, sampling is often sporadic and rarely reflects the overall population, particularly when concentrated on clinical isolates. This means that approaches that assume recent common ancestry are not applicable. Here we present a new approach to estimate the molecular clock rate in Campylobacter that draws on the popular probability conundrum known as the ‘birthday problem’. Using large genomic datasets and comparative genomic approaches, we use isolate pairs that share recent common ancestry to estimate the rate of nucleotide change for the population. Identifying synonymous and non-synonymous nucleotide changes, both within and outside of recombined regions of the genome, we quantify clock-like diversification to estimate synonymous rates of nucleotide change for the common pathogenic bacteria Campylobacter coli (2.4 x 10⁻⁶ s/s/y) and Campylobacter jejuni (3.4 x 10⁻⁶ s/s/y). Finally, using estimated total rates of nucleotide change, we infer the number of effective lineages within the sample time frame–analogous to a shared birthday–and assess the rate of turnover of lineages in our sample set over short evolutionary timescales. This provides a generalizable approach to calibrating rates in populations of environmental bacteria and shows that multiple lineages are maintained, implying that large-scale clonal sweeps may take hundreds of years or more in these species.     

L’apport de l’imagerie hybride TEMP/TDM dans la prise en charge du cancer différencié de la thyroïde

IntroductionSingle photon emission computed tomography combined with a low dose computed tomography (SPECT/CT), is a hybrid imaging integrating functional and anatomical data. The purpose of our study was to evaluate the contribution of the SPECT/CT over traditional planar imaging of patients with differentiated thyroid carcinoma (DTC).MethodsPost-therapy iodine 131 (¹³¹I) whole-body scan followed by cervico-thoracic SPECT/CT, were performed in 100 patients with DTC.ResultsAmong these 100 patients followed for a predominantly papillary DTC, planar imaging and SPECT/CT, were perfectly concordant in 70% of patients and discordant in the remaining 30%. The use of fusion imaging SPECT/CT compared to conventional planar imaging allowed us to correct our therapeutic approach in 27% (27/100 patients), according to the protocols of therapeutic management of our institute.ConclusionSPECT/CT is a hybrid imaging modality which provides better identification and more correct anatomic localization of the foci of radioiodine uptake with impact on therapeutic management.     

Demographic,seed and microsite limitations to seedling recruitment in semi-arid mine site restoration

Plant and Soil - Understanding limitations to plant recruitment is a key element in devising effective restoration of semi-arid ecosystems: only when these limitations are identified can management...     

Description and mapping of the resistance of DBA/2 mice to TNF-induced lethal shock

In our search for genes that inhibit the inflammatory effects of TNF without diminishing its antitumor capacities we found that, compared with C57BL/6 mice, DBA/2 mice exhibit a dominant resistance to TNF-induced lethality. Tumor-bearing (C57BL/6 x DBA/2)(BXD)F(1) mice completely survived an otherwise lethal TNF/IFN-gamma-antitumor therapy with complete regression of the tumor. This was not the case for C57BL/6 mice. Genetic linkage analysis revealed that TNF resistance is linked to a major locus on distal chromosome 6 and a minor locus on chromosome 17. Compared with littermate controls, chromosome substitution mice carrying a DBA/2 chromosome 6 in a C57BL/6 background were significantly protected against TNF and TNF/IFN-gamma, albeit less so than DBA/2 mice. Definition of a critical region of 13 Mb on chromosome 6 was the highest mapping resolution obtained. Further analysis of candidate genes may provide a powerful tool to control TNF-induced pathologies in humans.     

Fluorescent probes to evaluate the physiological state and activity of microbial biocatalysts: a guide for prokaryotic and eukaryotic investigation

Many fluorescent techniques are employed to evaluate the viability and activity of microbial cells used in biotechnology. These techniques are sometimes complex and the interpretation of results opened to misunderstanding. Moreover, new developments are constantly proposed especially concerning a more accurate evaluation of the state of the cells including eukaryotic microorganisms. This paper aims at presenting to biotechnologists unfamiliar with fluorescence the principles of these methods and the related possible pitfalls. It focuses on probes of the physical (integrity and fluidity) and energetical (intracellular pH and membrane potential) state of the cell membrane (bacterial and yeast cells) and presents also other probes (nucleic acids, respiration...) and new technical trends. The specificities of Gram-negative bacterial cells are also discussed.     

Reproductive biology of the annular seabream,Diplodus annularis (Linnaeus, 1758), in the Gulf of Gabes (Central Mediterranean)

Annular seabream, Diplodus annularis (Linnaeus, 1758), were caught off the coast of the Gulf of Gabes (Southern Tunisia, Central Mediterranean) between April 2008 and March 2010 by commercial catches. With a total 2066 specimens the fish ranged in size from 7.7 cm to 18.5 cm total length and from 7.5 g to 123.3 g in weight. Changes in biological parameters (weight, length, gonadosomatic index, hepatosomatic index and condition factor) were examined in order to provide information on the spawning period and reproductive cycle in the gulf. Overall sex ratio was 1 : 1.52 in favour of females. The reproductive season extends from March to June, with a spawning activity peak in May. Total length at sexual maturity was 10.5 ± 0.22 cm (males) and 10.6 ± 0.3 cm (females). The results of this study could help to establish a recommended minimum capture size.     

Influence of lipids on membrane assembly and stability of the potassium channel KcsA

A novel antibacterial peptide, moricin, isolated from the silkworm Bombyx mori, consists of 42 amino acids. It is highly basic and the amino acid sequence has no significant similarity to those of other antibacterial peptides. The 20 structures of moricin in methanol have been determined from two-dimensional 1H-nuclear magnetic resonance spectroscopic data. The solution structure reveals an unique structure comprising of a long alpha-helix containing eight turns along nearly the full length of the peptide except for four N-terminal residues and six C-terminal residues. The electrostatic surface map shows that the N-terminal segment of the alpha-helix, residues 5-22, is an amphipathic alpha-helix with a clear separation of hydrophobic and hydrophilic faces, and that the C-terminal segment of the alpha-helix, residues 23-36, is a hydrophobic alpha-helix except for the negatively charged surface at the position of Asp30. The results suggest that the amphipathic N-terminal segment of the alpha-helix is mainly responsible for the increase in permeability of the membrane to kill the bacteria.