Effect of dietary docosahexaenoic acid on biosynthesis of docosahexaenoic acid from alpha-linolenic acid in young rats

Docosahexaenoic acid (DHA), a crucial nervous system n-3 PUFA, may be obtained in the diet or synthesized in vivo from dietary alpha-linolenic acid (LNA). We addressed whether DHA synthesis is regulated by the availability of dietary DHA in artificially reared rat pups, during p8 to p28 development. Over 20 days, one group of rat pups was continuously fed deuterium-labeled LNA (d5-LNA) and no other n-3 PUFA (d5-LNA diet), and a second group of rat pups was fed a d5-LNA diet with unlabeled DHA (d5-LNA + DHA diet). The rat pups were then euthanized, and the total amount of deuterium-labeled docosahexaenoic acid (d5-DHA) (synthesized DHA) as well as other n-3 fatty acids present in various body tissues, was quantified. In the d5-LNA + DHA group, the presence of dietary DHA led to a marked decrease (3- to 5-fold) in the total amount of d5-DHA that accumulated in all tissues that we examined, except in adipose. Overall, DHA accretion from d5-DHA was generally diminished by availability of dietary preformed DHA, inasmuch as this was found to be the predominant source of tissue DHA. When preformed DHA was unavailable, d5-DHA and unlabeled DHA were preferentially accreted in some tissues along with a net loss of unlabeled DHA from other organs.     

Genome-Wide Analysis of the Fusarium oxysporum mimp Family of MITEs and Mobilization of Both Native and De Novo Created mimps

We have performed a genome-wide analysis of the mimp family of miniature inverted-repeat transposable elements, taking advantage of the recent release of the F. oxysporum genome sequence. Using different approaches, we detected 103 mimp elements, corresponding to 75 nonredundant copies, half of which are located on a single small chromosome. Phylogenetic analysis identified at least six subfamilies, all remarkably homogeneous in size and sequence. Based on high sequence identity in the terminal inverted repeats (TIRs), mimp elements were connected to different impala members. To gain insights into the mechanisms at the origin and amplification of mimps, we studied the potential of impala to cross-mobilize different mimps, native but also created de novo by inserting a short DNA segment between two TIRs. Our results show that TIR sequences are the main requirement for mobilization but that additional parameters in the internal region are likely to influence transposition efficiency. Finally, we show that integration site preference of native versus newly transposed mimps greatly varies in the host genomes used in this study. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Nucleotide sequences of novel mimp3 and mimp4 elements are available under GenBank accession numbers EU833100 and EU833101, respectively. Coordinates of mimp5, mimp6 and of non-classified mimp copies are indicated in Supplementary Table 1.     

Sensitive biochemical aggregate detection reveals aggregation onset before symptom development in cellular and murine models of Huntington's disease

A CAG-repeat gene expansion translated into a pathogenic polyglutamine stretch at the N-terminus of huntingtin triggers Huntington's Disease. Mutated huntingtin is predicted to adopt toxic properties mainly if aggregation-prone N-terminal fragments are released by proteolysis. Huntingtin-aggregates are indeed a major hallmark of this disorder and could represent useful markers of disease-onset or progression. We designed a simple method for qualitative and quantitative characterization of aggregates. For this, we analyzed samples from in vitro and in vivo Huntington's Disease models by agarose gel electrophoresis and showed that in the brain of transgenic mice huntingtin-aggregates became larger as a function of disease progression. This appears to be a property of cytoplasmic but not nuclear aggregates. In cell cultures, treatment with Congo Red inhibited aggregate growth but not total load. Finally, we showed that in primary striatal neurons and in brains of R6/2 and Hdh Q150 mice, the presence of aggregates preceded initiation of any other functional deficits. This observation argues for a pathogenic role of huntingtin-aggregation in Huntington's Disease. Our results emphasize that thorough analysis of huntingtin metabolism and aggregation is now feasible, thus significantly improving the power of studies assessing therapies designed to lower huntingtin levels or to interfere with its aggregation.     

Inhibition by Dications of in vitro growth of Leishmania major and Leishmania tropica: causative agents of old world cutaneous leishmaniasis

Old World cutaneous leishmaniasis is caused by infection with Leishmania major and Leishmania tropica. Pentamidine and related dications exhibit broad spectrum antiprotozoal activity. Based on the previously reported efficacy of these compounds against related organisms, 18 structural analogs of pentamidine were evaluated for in vitro antileishmanial activity, using pentamidine as the standard reference drug for comparison. Furan analogs and reversed amidine compounds were examined for activity against L. major and L. tropica promastigotes. The most active compounds against both Leishmania species were in the reversed amidine series. DB745 and DB746 exhibited the highest activity against L. major and DB745 was the most active compound against L. tropica. Both of these compounds exhibited 50% inhibitory concentrations (IC50) below 1 nM for L. major. Ten reversed amidines were also tested for their ability to inhibit growth in an axenic amastigote model. Nine of 10 reversed amidine analogs were active at concentrations below 1 nM. These results justify further study of dicationic compounds as potential new agents for treating cutaneous leishmaniasis.     

Causal inference in biomolecular pathways using a Bayesian network approach and an Implicit method

We introduce here the concept of Implicit networks which provide, like Bayesian networks, a graphical modelling framework that encodes the joint probability distribution for a set of random variables within a directed acyclic graph. We show that Implicit networks, when used in conjunction with appropriate statistical techniques, are very attractive for their ability to understand and analyze biological data. Particularly, we consider here the use of Implicit networks for causal inference in biomolecular pathways. In such pathways, an Implicit network encodes dependencies among variables (proteins, genes), can be trained to learn causal relationships (regulation, interaction) between them and then used to predict the biological response given the status of some key proteins or genes in the network. We show that Implicit networks offer efficient methodologies for learning from observations without prior knowledge and thus provide a good alternative to classical inference in Bayesian networks when priors are missing. We illustrate our approach by an application to simulated data for a simplified signal transduction pathway of the epidermal growth factor receptor (EGFR) protein.     

The effect of apolipoprotein E polymorphism on plasma cholesteryl ester transfer protein activity in type 2 diabetic patients

We studied the relationship between apo E polymorphism and cholesteryl ester transfer protein (CETP) activity in 127 type 2 diabetic patients who did not take lipid lowering drugs. Furthermore, we studied the relationship between apo E and cholesteryl ester transfer protein (CETP) in modulating plasma triglyceride and HDLcholesterol. Apo E genotypes were determined by PCR-RFLP, and CETP activity was measured using an exogenous way. Our results showed that the CETP activity increased significantly in the E2 carrier group compared to E4 carriers and E3/E3 homozygous (84.7 ± 43.9 vs. 62.5 ± 35.9 vs. 52.6 ± 23.6 nmol CE/ml/2h, respectively; p = 0.015). However, there was no association between apo E polymorphism and lipid parameter variations. Even after adjustment for CETP activity, the results remained unchanged, showing that CETP did not step in the relationship between apo E and lipid parameter variations. In conclusion there is an association between apo E polymorphism and CETP activity, and this association did not affect the relationship between apo E polymorphism and triglyceride and HDLcholesterol concentrations. Published in Russian in Molekulyarnaya Biologiya, 2008, Vol. 42, No. 6, pp. 931–935. The text was submitted by the authors in English.     

A simple, integrative assay to quantify nutritional quality of browses for herbivores

Many regard the concentrations of nitrogen (N), tannins and plant cell wall constituents (fibre) as key indicators of food quality and habitat suitability for browsing herbivores; yet there is no method for measuring their combined effects. We have developed a simple in vitro assay for measuring the effects of tannins and fibre on N availability in browse. We determined the effects of tannins by measuring the polyethylene glycol (PEG)-binding capacity (PEG-BC) of Eucalyptus leaf samples, followed by a two-stage in vitro digestion with pepsin and cellulase to determine the digestibility of dry matter and N. There was a significant relationship between concentrations of digestible N and the PEG-BC of the leaves. Furthermore, adding PEG significantly improved the digestibility of N. Our results concur with in vivo observations from several mammalian species. This suggests that our method is effective for measuring the nutritional quality of browse and the benefits of adding PEG, providing some index of the detrimental effects of tannins. We further simplified the assay by removing the PEG step, allowing us to quickly analyse samples in bulk. Nevertheless, this simplified method is still not practical for analysing the many samples necessary to compare the nutritional values of different tracts of forest. We used near-infrared reflectance spectroscopy to produce calibration equations and predicted total and digestible N in 322 trees at eleven sites. Both within and between sites, we found a wide variation in concentrations of digestible N but a much lower variation in total N, with either no relationship or poor relationships between the two measures. This confirms the variability in the nutritional quality of eucalypt forests, which may explain the distribution and abundance of mammalian herbivores. Thus, our assay provides a useful tool for understanding how food resources influence herbivore populations at different scales. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.