Alteration of plasma phospholipid fatty acid profile in patients with septic shock

In septic shock patients, alterations of plasma phospholipid fatty acid profile have never been described. The purpose of this monocentric, non-interventional, observational prospective study was to describe this fatty acid profile in the early phase of septic shock in intensive care unit. Thirty-seven adult patients with septic shock were included after the first day of stay in intensive care unit, before any form of artificial nutritional support. Plasma phospholipid fatty acid composition was determined by gas chromatography. All biological data from patients with septic shock were compared with laboratory reference values. Patients presented hypocholesterolemia and hypertriglyceridemia. They had low concentrations of phospholipid fatty acids specifically n-6 and n-3 polyunsaturated fatty acids (PUFAs) with a high n-6/n-3 ratio. Plasma phospholipid PUFA concentrations were strongly correlated with cholesterolemia. PUFAs/SFAs (saturated fatty acids) and PUFAs/MUFAs (monounsaturated fatty acids) ratios were low because of low percentage of n-6 and n-3 PUFAs and high percentage of SFAs and MUFAs. Low levels of plasma long chain PUFAs (≥20 carbons) were significantly associated with mortality at 28th day. In conclusion, plasma phospholipid FA profile of septic patients is very characteristic, close to that of acute respiratory distress syndrome and mortality is associated with long chain PUFA decrease. This profile could be explained by numerous non-exclusive physio-pathological processes 1) an activation of hepatic de novo lipogenesis that could contribute to hepatic steatosis, 2) an elevated adipose tissue lipolysis, 3) an increased free radical attack of FA by oxidative stress, 4) an over-production of inflammatory lipid mediators.     

Translational studies on regulation of brain docosahexaenoic acid (DHA) metabolism in vivo

One goal in the field of brain polyunsaturated fatty acid (PUFA) metabolism is to translate the many studies that have been conducted in vitro and in animal models to the clinical setting. Doing so should elucidate the role of PUFAs in the human brain, and effects of diet, drugs, disease and genetics on this role. This review discusses new in vivo radiotracer kinetic and neuroimaging techniques that allow us to do this, with a focus on docosahexaenoic acid (DHA). We illustrate how brain PUFA metabolism is influenced by graded reductions in dietary n-3 PUFA content in unanesthetized rats. We also show how kinetic tracer techniques in rodents have helped to identify mechanisms of action of mood stabilizers used in bipolar disorder, how DHA participates in neurotransmission, and how brain DHA metabolism is regulated by calcium-independent iPLA₂β. In humans, regional rates of brain DHA metabolism can be quantitatively imaged with positron emission tomography following intravenous injection of [1-¹¹C]DHA.     

Effect of molybdenum on secondary metabolic process of glycyrrhizic acid in Glycyrrhiza uralensis Fisch.

A pot experiment was conducted to investigate into effects of molybdenum (Mo) on the secondary metabolic process of glycyrrhizic acid (GA). One-year-old seedlings were grown in pots with washed vermiculite and sand. Hoagland nutrition solution was irrigated with four concentrations: 0, 0.52, 5.2 and 10.4 mg L⁻¹. The accumulations of GA and its biosynthetic precursors (β-amyrin and squalene) and then expression of the key synthase (β-amyrin synthase, β-AS) were studied on 35, 70 and 105 d. In the early stage, that was on the 35 and 70 d, the contents of squalene and GA, and the expression of β-AS gene under 0.52 and 5.2 mg L⁻¹ Mo treatments were significantly higher than that under 0 and 10.4 mg L⁻¹ Mo. There was a contrary result of β-amyrin. However, the content of squalene under 0 mg L⁻¹ Mo was the highest on 105 d. Thus, it suggested an appropriate concentration of Mo could promote the accumulation of GA, by affecting the biosynthetic process of GA at a certain time. Practically, the time and amount of application of Mo on Glycyrrhiza uralensis should be the noted.     

Decomposition of sugarcane bagasse with lignocellulose-derived thermotolerant and thermoresistant Penicillia and Aspergilli

To promote the decomposition of sugarcane bagasse (SCB) for conversion into value-added products and to reduce waste, the capability of fungal mixes (FMs) to degrade SCB was examined. A total of 169 isolates from SCB and non-SCB were categorized as thermotolerant and thermoresistant. Thirty-six fungal candidates were screened for the presence of polyphenol oxidase, endoglucanase (EDN) and xylanase (XLN) activities, and EDN and XLN activities were quantitated. Five identified isolates (Aspergillus flavus AG10; Aspergillus niger AG68 & NB23; and Penicillium citrinum AG93 & AG140) were selected as the best enzyme producers, and 15 moderately to highly xylolytic, cellulolytic and ligninolytic isolates were added to construct FMs. Using a Taguchi design, the top ten reducing sugar-producing FMs (no. 12 showed the maximum amount of reducing sugar, at 2.11 mg g⁻¹, followed by no. 7, 15, 2, 16, 11, 13, 6, 4, & 8) were selected as potential agents for decomposition durations of 1, 2 and 3 months. The maximum decrease in SCB materials compared with the control was generated by FM 6 (9.08% cellulose reduction); FM 13 (21.03% hemicellulose reduction); and FM 16 (9.21% lignin reduction). These results indicate the potential use of SCB as a substrate for synergistic FMs. These FMs could be applied to the large-scale composting of SCB and other related agricultural residues, thus improving the biological pretreatment of lignocellulose.     

The ACBP gene family in Rhodnius prolixus: Expression,characterization and function of RpACBP-1

The acyl-CoA-binding proteins (ACBP) constitute a family of conserved proteins that bind acyl-CoA with high affinity and protect it from hydrolysis. Thus, ACBPs may have essential roles in basal cellular lipid metabolism. The genome of the insect Rhodnius prolixus encodes five ACBP genes similar to those described for other insect species. The qPCR analysis revealed that these genes have characteristic expression profiles in insect organs, suggesting that they have specific roles in insect physiology. Recombinant RpACBP-1 was able to bind acyl-CoA in an in vitro gel-shift assay. Moreover, heterologous RpACBP-1 expression in acb1Δ mutant yeast rescued the multi-lobed vacuole phenotype, indicating that RpACBP-1 acts as a bona fide acyl-CoA-binding protein. RpACBP-1 knockdown using RNAi caused triacylglycerol accumulation in the insect posterior midgut and a reduction in the number of deposited eggs. The amount of stored triacylglycerol was reduced in flight muscle, and the incorporation of fatty acids in cholesteryl esters was increased in the fat body. These results showed that RpACBP-1 participates in several lipid metabolism steps in R. prolixus.     

Sternal gland structures in males of bean flower thrips,Megalurothrips sjostedti,and Poinsettia thrips,Echinothrips americanus,in comparison with those of western flower thrips,Frankliniella occidentalis (Thysanoptera: Thripidae)

Sternal pores are important features for identification of male thrips, especially within the subfamily Thripinae. They vary in shape, size and distribution even between species of one genus. Their functional role is speculated to be that of sex- and/or aggregation pheromone production. Yet, sexual aggregations are not reported in Echinothrips americanus, known to have sternal pores, while we observed aggregations in Megalurothrips sjostedti, previously reported to lack them.We examined the sternal glands and pores of the thripine species E. americanus and M. sjostedti males, in comparison with those of Frankliniella occidentalis using light microscopy, as well as scanning and transmission electron microscopy. Pore plates of F. occidentalis were ellipsoid and medial on sternites III–VII, while in E. americanus they were distributed as multiple micro pore plates on sternites III–VIII. In M. sjostedti they appeared as an extremely small pore in front of the posterior margin of each of sternites IV–VII. Pore plate and pore plate area were distributed similarly on sternites III–VII in F. occidentalis. However, in E. americanus the total pore plate area increased significantly from sternites III to VIII. Ultrastructure of cells associated with sternal glands showed typical characteristics of gland cells that differ in size, shape and number. The function of sternal glands is further discussed on the basis of morphological comparisons with other thrips species.     

Shifts in thermoregulatory strategy during ontogeny in harp seals (Pagophilus groenlandicus)

Heat balance can be difficult for young and/or small animals in polar regions because environmental conditions in combination with small body size or physiological immaturity can increase heat loss. We investigated how thermoregulatory patterns change with ontogeny in 5 age classes of harp seal (Pagophilus groenlandicus) from birth to post-molt to further understand the timing of thermoregulatory development in relation to their potential vulnerability to ongoing fluctuations in the extent and stability of Arctic pack ice. We measured changes in the amount, conductivity, and resistance of the seal pups׳ insulative layers (blubber and fur), the potential for endogenous heat-generation by shivering (muscle enzyme activity), and nonshivering thermogenesis (NST; brown adipose tissue (BAT) uncoupling protein 1 (UCP1) expression and mitochondrial density). There was no significant difference in blubber conductivity among age classes, though the amount of blubber insulation significantly increased from birth to weaning. Pelage conductivity was low (0.12±0.01 W m⁻¹ °C⁻¹) except in 9-day old pups (0.40±0.08 W m⁻¹ °C⁻¹); the significantly higher conductivity may signal the beginning of the molt, and this age group may be the most vulnerable to early water entry. Citrate synthase activity significantly increased (49.68±3.26 to 75.08±3.52 μmol min⁻¹ g wet weight⁻¹) in the muscle; however it is unlikely that increasing a single enzyme greatly impacts heat generation. BAT of younger pups contained UCP1, though expression and mitochondrial density quickly declined, and the ability of pups to produce heat via NST was lost by weaning. While total thermal resistance did not differ, neonatal and early nursing animals gained the majority of their thermal resistance from lanugo (82.5±0.03%); however, lanugo is not insulative when wet, and NST may be important to maintain euthermia and dry the coat if early immersion in water occurs. By late nursing, blubber seems sufficient as insulation (75.87±0.01% of resistance after 4 weeks), but high conductivity of fur may be responsible for retention of UCP1 expression. Weaned animals rely on blubber insulation, and no longer need NST, as wetted fur is no longer a threat to euthermia.     

Effect of resveratrol on vitrified in vitro produced bovine embryos: Recovering the initial quality

Although vitrification is the current routine method for human embryo cryopreservation, it may cause detrimental effects. The aim of this study was to evaluate the effect of supplementing in vitro culture (IVC) media and/or vitrification solutions (VS) with Resveratrol on the presence of apoptotic markers, reactive oxygen species (ROS) level, glutathione (GSH) content and relative gene abundance. Abattoir-derived oocytes were matured and fertilized in vitro according to a standard procedure. Zygotes were cultured in IVC medium supplemented with or without 0.5 μM Resveratrol (C^R, C⁻ respectively). On day 7, blastocysts were vitrified using the minimum volume vitrification method supplementing VS with (C⁻V^R, C^RV^R) or without (C^–V^-, C^RV⁻) 0.5 μM Resveratrol. After warming, embryonic quality parameters were evaluated. Survival rates were significantly lower in C^RV^R group compared with C^RV⁻ group, but no differences in hatching rate were observed between groups. Vitrification/warming process did not alter total cell number or the presence of apoptotic or dead cells, but C^RV⁻ and C^RV^R groups presented a significant increase in dead cells (P < 0.05 by ANOVA). Resveratrol supplementation in VS (C⁻V^R) restored GSH content (P < 0.05) to the level found in the C^R group. Vitrification/warming process significantly increased the expression of FOXO3A, PNPLA2, BCL2L1 and BAX genes (P < 0.05). Resveratrol addition to IVC medium or VS partially compensated this increase for FOXO3A and PNPLA2 (P < 0.05) but not for BCL2L1 and BAX. In conclusion, supplementation of IVC media or VS with 0.5 μM resveratrol may help embryos to partially restore the initial quality they had before the cryopreservation process.     

Enhanced intestinal epithelial barrier health status on European sea bass (Dicentrarchus labrax) fed mannan oligosaccharides

The study assesses the effects of dietary mannan oligosaccharides (MOS) in European sea bass (Dicentrarchus labrax) posterior intestinal lipid class composition and its possible relation to the potential prostaglandins production and Gut Associated Lymphoid Tissue (GALT) stimulation.Fish were fed 4 g kg^?1 MOS (Bio-Mos^® Aquagrade, Alltech, Inc., USA) for eight weeks. Fish fed MOS presented higher (P ≤ 0.05) weight gain, total length, and specific and relative growth rates than fish fed the control diet. Stimulated posterior gut of fish fed MOS showed higher (P ≤ 0.05) prostaglandins production than fish fed the control diet. Lipid class analyses of posterior gut revealed a reduction (P ≤ 0.05) in the neutral lipid fraction in fish fed MOS compared to fish fed the control diet, particularly due to a reduction (P ≤ 0.05) in triacylglycerols content. The polar lipid fraction increased (P ≤ 0.05) in fish fed MOS compared to fish fed the control diet, mainly due to an increase (P ≤ 0.05) in phosphatidylethanolamine and phosphatidylcoline contents.Light microscopy of posterior gut revealed increased number or goblet cells as well as higher level of infiltrated eosinophilic granulocytes for fish fed MOS. Transmission electron microscopy qualitative observations revealed a better preserved cytoarchitecture of the intestinal epithelial barrier in the posterior gut of fish fed MOS. Posterior gut of fish fed MOS presented more densely packed non-damaged enterocytes, better preserved tight junctions structure, healthier and more organized microvilli, and a higher presence of infiltrated lymphocytes and granulocytes compared fish fed the control diet.The present study indicates that dietary MOS enhances European sea bass posterior gut epithelial defense by increasing membrane polar lipids content in relation to a stimulation of the eicosanoid cascade and GALT, promoting posterior gut health status.     

Optimization of the cryopreservation of biological resources,Toxoplasma gondii tachyzoites,using flow cytometry

The conservation of Toxoplasma gondii strains isolated from humans and animals is essential for conducting studies on Toxoplasma. Conservation is the main function of the French Biological Toxoplasma Resource Centre (BRC Toxoplasma, France, http://www.toxocrb.com/). In this study, we have determined the suitability of a standard cryopreservation methodology for different Toxoplasma strains using the viability of tachyzoites assayed by flow cytometry with dual fluorescent labelling (calcein acetoxymethyl ester and propidium iodide) of tachyzoites. This method provides a comparative quantitative assessment of viability after thawing. The results helped to define and refine quality criteria before tachyzoite cryopreservation and optimization of the cryopreservation parameters. The optimized cryopreservation method uses a volume of 1.0 mL containing 8 × 10⁶ tachyzoites, in Iscove's Modified Dulbecco's Medium (IMDM) containing 10% foetal calf serum (FCS). The cryoprotectant additive is 10% v/v Me₂SO without incubation. A cooling rate of ∼1 °C/min to −80 °C followed, after 48 h, by storage in liquid nitrogen. Thawing was performed using a 37 °C water bath that produced a warming rate of ∼100 °C/min, and samples were then diluted 1:5 in IMDM with 5% FCS, and centrifuged and resuspended for viability assessment.     

Peripheral arterial stiffness is associated with higher baseline plasma uric acid: A prospective cohort study

This prospective cohort study aimed at identifying association between uric acid (UA) and peripheral arterial stiffness. A prospective cohort longitudinal study was performed according to an average of 4.8 years’ follow-up. The demographic data, anthropometric parameters, peripheral arterial stiffness (carotid-radial pulse-wave velocity, cr-PWV) and biomarker variables including UA were examined at both baseline and follow-up. Pearson’s correlations were used to identify the associations between UA and peripheral arterial stiffness. Further logistic regressions were employed to determine the associations between UA and arterial stiffness. At the end of follow-up, 1447 subjects were included in the analyses. At baseline, cr-PWV (r = 0.200, p < 0.001) was closely associated with UA. Furthermore, the follow-up cr-PWV (r = 0.145, p < 0.001) was also strongly correlated to baseline UA in Pearson’s correlation analysis. Multiple regressions also indicated the association between follow-up cr-PWV (β = 0.493, p = 0.013) and baseline UA level. Logistic regressions revealed that higher baseline UA level was an independent predictor of arterial stiffness severity assessed by cr-PWV at follow-up cross-section. Peripheral arterial stiffness is closely associated with higher baseline UA level. Furthermore, a higher baseline UA level is an independent risk factor and predictor for peripheral arterial stiffness.     

Genetic factors in individual radiation sensitivity

Cancer risk and radiation sensitivity are often associated with alterations in DNA repair, cell cycle, or apoptotic pathways. Interindividual variability in mutagen or radiation sensitivity and in cancer susceptibility may also be traced back to polymorphisms of genes affecting e.g. DNA repair capacity. We studied possible associations between 70 polymorphisms of 12 DNA repair genes with basal and initial DNA damage and with repair thereof. We investigated DNA damage induced by ionizing radiation in lymphocytes isolated from 177 young lung cancer patients and 169 cancer-free controls. We also sought replication of our findings in an independent sample of 175 families (in total 798 individuals). DNA damage was assessed by the Olive tail moment (OTM) of the comet assay. DNA repair capacity (DRC) was determined for 10, 30 and, 60 min of repair.Genes involved in the single-strand-repair pathway (SSR; like XRCC1 and MSH2) as well as genes involved in the double-strand-repair pathway (DSR; like RAD50, XRCC4, MRE11 and ATM) were found to be associated with DNA damage. The most significant association was observed for marker rs3213334 (p = 0.005) of XRCC1 with basal DNA damage (B), in both cases and controls. A clear additive effect on the logarithm of OTM was identified for the marker rs1001581 of the same LD-block (p = 0.039): B_CC = −1.06 (95%-CI: −1.16 to −0.96), B_CT = −1.02 (95%-CI: −1.11 to −0.93) and B_TT = −0.85 (95%-CI: −1.01 to −0.68). In both cases and controls, we observed significantly higher DNA basal damage (p = 0.007) for carriers of the genotype AA of marker rs2237060 of RAD50 (involved in DSR). However, this could not be replicated in the sample of families (p = 0.781). An alteration to DRC after 30 min of repair with respect to cases was observed as borderline significant for marker rs611646 of ATM (involved in DSR; p = 0.055), but was the most significant finding in the sample of families (p = 0.009).Our data indicate that gene variation impacts measurably on DNA damage and repair, suggesting at least a partial contribution to radiation sensitivity and lung cancer susceptibility.     

Ingestion of the epoxide hydrolase inhibitor AUDA modulates immune responses of the mosquito,Culex quinquefasciatus during blood feeding

Epoxide hydrolases (EHs) are enzymes that play roles in metabolizing xenobiotic epoxides from the environment, and in regulating lipid signaling molecules, such as juvenile hormones in insects and epoxy fatty acids in mammals. In this study we fed mosquitoes with an epoxide hydrolase inhibitor AUDA during artificial blood feeding, and we found the inhibitor increased the concentration of epoxy fatty acids in the midgut of female mosquitoes. We also observed ingestion of AUDA triggered early expression of defensin A, cecropin A and cecropin B2 at 6 h after blood feeding. The expression of cecropin B1 and gambicin were not changed more than two fold compared to controls. The changes in gene expression were transient possibly because more than 99% of the inhibitor was metabolized or excreted at 42 h after being ingested. The ingestion of AUDA also affected the growth of bacteria colonizing in the midgut, but did not affect mosquito longevity, fecundity and fertility in our laboratory conditions. When spiked into the blood, EpOMEs and DiHOMEs were as effective as the inhibitor AUDA in reducing the bacterial load in the midgut, while EETs rescued the effects of AUDA. Our data suggest that epoxy fatty acids from host blood are immune response regulators metabolized by epoxide hydrolases in the midgut of female mosquitoes, inhibition of which causes transient changes in immune responses, and affects growth of microbes in the midgut.     

Effect of molecular weight of condensed tannins from warm-season perennial legumes on ruminal methane production in vitro

The objectives of the present study were to determine if the molecular weight of condensed tannins (CT) from warm-season perennial legumes affects the biological activity of CT relative to suppression of methane (CH₄) production by ruminants, and to identify potential North American native forage plants to use for mitigation of enteric CH₄ emission. Eight North American native warm-season perennial legumes were evaluated: Leucaena retusa Benth. (littleleaf leadtree), Desmanthus illinoensis (Michx.) MacMill. Ex B.L. Rob. & Fernald (Illinois bundleflower), Lespedeza stuevei Nutt. (tall lespedeza), Mimosa strigillosa Torr. & A. Gray (powderpuff), Neptunia lutea (Leavenworth) Benth. (yellow puff), two ecotypes of Acacia angustissima var. hirta (Nutt.) B.L. Rob (prairie acacia), and Desmodium paniculatum (L.) DC. var. paniculatum (panicledleaf ticktrefoil). Two introduced legumes were also included: Arachis glabrata Benth. (rhizoma peanut) and Lespedeza cuneata (Dum. Cours.) G. Don (sericea lespedeza). Forages were fermented with cattle rumen fluid for 48 h anaerobically using an in vitro gas production technique. D. paniculatum, L. stuevei, and M. strigillosa were high in CT, ranging from 11.7 to 12.5%. D. illinoensis, L. cuneata, N. lutea, and two ecotypes of A. angustissima var. hirta had less CT (P < 0.05), ranging from 8.1 to 8.9%, whereas L. retusa and A. glabrata had the least CT (P < 0.05), measuring 3.2 and 0.5%, respectively. Weight-average molecular weight (M_W) of CT ranged from 1483 Da for L. cuneata to 552 Da for L. stuevei. In vitro CH₄ production was greatest for L. retusa and A. glabrata at 40.7 mg/g DM and 38.2 mg/g DM, respectively. The least amount of in vitro CH₄ was produced by fermentation of two ecotypes of A. angustissima var. hirta, which measured 0.8 and 0.6 mg/g DM, respectively. In vitro CH₄ production regressed on CT M_W resulted in a R² of 0.0009 (P = 0.80), strongly suggesting that CT M_W does not explain the biological activity of in vitro CH₄ production by the forage legumes surveyed. Five of the seven North American native warm-season perennial legumes have promise for use in ruminant diets for the purpose of CH₄ emission mitigation.     

Epoxide hydrolase activities and epoxy fatty acids in the mosquito Culex quinquefasciatus

Culex mosquitoes have emerged as important model organisms for mosquito biology, and are disease vectors for multiple mosquito-borne pathogens, including West Nile virus. We characterized epoxide hydrolase activities in the mosquito Culex quinquefasciatus, which suggested multiple forms of epoxide hydrolases were present. We found EH activities on epoxy eicosatrienoic acids (EETs). EETs and other eicosanoids are well-established lipid signaling molecules in vertebrates. We showed EETs can be synthesized in vitro from arachidonic acids by mosquito lysate, and EETs were also detected in vivo both in larvae and adult mosquitoes by LC-MS/MS. The EH activities on EETs can be induced by blood feeding, and the highest activity was observed in the midgut of female mosquitoes. The enzyme activities on EETs can be inhibited by urea-based inhibitors designed for mammalian soluble epoxide hydrolases (sEH). The sEH inhibitors have been shown to play diverse biological roles in mammalian systems, and they can be useful tools to study the function of EETs in mosquitoes. Besides juvenile hormone metabolism and detoxification, insect epoxide hydrolases may also play a role in regulating lipid signaling molecules, such as EETs and other epoxy fatty acids, synthesized in vivo or obtained from blood feeding by female mosquitoes.     

Bovine ovarian cells have (pro)renin receptors and prorenin induces resumption of meiosis in vitro

The discovery of a receptor that binds prorenin and renin in human endothelial and mesangial cells highlights the possible effect of renin-independent prorenin in the resumption of meiosis in oocytes that was postulated in the 1980s.This study aimed to identify the (pro)renin receptor in the ovary and to assess the effect of prorenin on meiotic resumption. The (pro)renin receptor protein was detected in bovine cumulus-oocyte complexes, theca cells, granulosa cells, and in the corpus luteum. Abundant (pro)renin receptor messenger ribonucleic acid (mRNA) was detected in the oocytes and cumulus cells, while prorenin mRNA was identified in the cumulus cells only. Prorenin at concentrations of 10⁻¹⁰, 10⁻⁹, and 10⁻⁸ M incubated with oocytes co-cultured with follicular hemisections for 15 h caused the resumption of oocyte meiosis. Aliskiren, which inhibits free renin and receptor-bound renin/prorenin, at concentrations of 10⁻⁷, 10⁻⁵, and 10⁻³ M blocked this effect (P < 0.05). To determine the involvement of angiotensin II in prorenin-induced meiosis resumption, cumulus-oocyte complexes and follicular hemisections were treated with prorenin and with angiotensin II or saralasin (angiotensin II antagonist). Prorenin induced the resumption of meiosis independently of angiotensin II. Furthermore, cumulus-oocyte complexes cultured with forskolin (200 μM) and treated with prorenin and aliskiren did not exhibit a prorenin-induced resumption of meiosis (P < 0.05). Only the oocytes’ cyclic adenosine monophosphate levels seemed to be regulated by prorenin and/or forskolin treatment after incubation for 6 h. To the best of our knowledge, this is the first study to identify the (pro)renin receptor in ovarian cells and to demonstrate the independent role of prorenin in the resumption of oocyte meiosis in cattle.     

Transposition burst of mariner-like elements in the sequenced genome of Rhodnius prolixus

Transposable elements (TEs) are widespread in insect's genomes. However, there are wide differences in the proportion of the total DNA content occupied by these repetitive sequences in different species. We have analyzed the TEs present in R. prolixus (vector of the Chagas disease) and showed that 3.0% of this genome is occupied by Class II TEs, belonging mainly to the Tc1-mariner superfamily (1.65%) and MITEs (1.84%). Interestingly, most of this genomic content is due to the expansion of two subfamilies belonging to: irritans himar, a well characterized subfamily of mariners, and prolixus1, one of the two novel subfamilies here described. The high amount of sequences in these subfamilies suggests that bursts of transposition occurred during the life cycle of this family. In an attempt to characterize these elements, we performed an in silico analysis of the sequences corresponding to the DDD/E domain of the transposase gene. We performed an evolutionary analysis including network and Bayesian coalescent-based methods in order to infer the dynamics of the amplification, as well as to estimate the time of the bursts identified in these subfamilies. Given our data, we hypothesized that the TE expansions occurred around the time of speciation of R. prolixus around 1.4 mya. This suggestion lays on the “Transposon Model” of TE evolution, in which the members of a TE population that are replicative active are present at multiple loci in the genome, but their replicative potential varies, and of the “Life Cycle Model” that states that when present-day TEs have been involved in amplification bursts, they share an ancestral copy that dates back to this initial amplification.