Gaining insights in the nutritional metabolism of amphibians : analyzing body nutrient profiles of the African clawed frog, Xenopus laevis

Whole bodies of Xenopus laevis (n = 19) were analysed for chemical composition and morphometrics. The nutrient profile (macronutrients, amino acids, fatty acids and minerals) was evaluated by sex; interactions among variables with body weights and lengths, and comparisons made with different species of marine and fresh water fish. Significant differences were found in morphometric measurements, water content, several minerals and fatty acids between sexes of X. laevis. Amino acid profiles differed in methionine, proline and cysteine, which could underlie different metabolic pathways in frogs when compared to fish. In addition, fatty acid profiles revealed more monounsaturated and n - 6 polyunsaturated fatty acids in frogs than in fish, more similar to values reported for terrestrial than aquatic vertebrates. Important interactions were also found between body measurements and fat, calcium, and phosphorus, as well as between essential and non-essential amino acids. The results indicate that frogs might have particular biochemical pathways for several nutrients, dependent on sex and linked to body weight, which ultimately could reflect specific nutrient needs

Diabetes mellitus and the metabolic syndrome do not abolish, but might reduce, the cardioprotective effect of ischemic postconditioning

ObjectiveIschemic preconditioning fails to protect the diabetic heart against lethal reperfusion injury. Because the pathways of ischemic pre- and postconditioning partially overlap, we evaluated the cardioprotective effect of ischemic postconditioning in mouse models of type 2 diabetes (ObOb) and the metabolic syndrome (DKO).MethodsMice (C57BL/6J, ObOb, and DKO; aged 24 weeks; n = 24, n = 28, and n = 18, respectively) underwent reperfusion after 30 minutes of coronary occlusion with or without ischemic postconditioning (3 cycles of 10 seconds reperfusion–reocclusion). Left ventricular contractility and infarct size were assessed 60 minutes later with pressure conductance analysis and 2,3,5-triphenyl-tetrazolium chloride staining, respectively. In a second cohort (C57BL/6J and DKO; aged 12 weeks; n = 31 and n = 24, respectively) cardiac cine magnetic resonance imaging was performed after 1 and 10 weeks, followed by pressure conductance analysis and Sirius red staining.ResultsIn the C57BL6/J mice, the infarct size was lower (40%, P < 10−5) and the load independent preload recruitable stroke work was greater after ischemic postconditioning (P < .05). In the ObOb and DKO mice, ischemic postconditioning reduced the infarct size by 24% (P < 10−5). In the C57BL/6J mice, the ejection fraction was greater and the myocardial mass was lower 10 weeks after ischemic postconditioning (P < .05). Tagging grid deformation was increased after ischemic postconditioning in both infarcted and remote areas. After ischemic postconditioning, the survival and ejection fraction were greater in the DKO mice (67% vs 17% and 44% ± 11% vs 59% ± 2%, P < .05 for both), and the collagen content was lower for both C57BL/6J and DKO mice (P < .05 for both).ConclusionsThe cardioprotective effect of ischemic postconditioning was sustained in C57BL/6J mice after 10 weeks and protected against adverse left ventricular remodeling. In mouse models of type 2 diabetes, protection against lethal reperfusion injury is present, leading to increased survival after ischemia and reperfusion

Evolution of antibody landscape and viral envelope escape in an HIV-1 CRF02_AG infected patient with 4E10-like antibodies

<p>Abstract</p> <p>Background</p> <p>A minority of HIV-1 infected individuals develop broad cross-neutralizing (BCN) plasma antibodies that are capable of neutralizing a spectrum of virus variants belonging to different HIV-1 clades. The aim of this study was to identify the targeted epitopes of an individual with BCN plasma antibodies, referred to as ITM4, using peptide phage display. This study also aimed to use the selected mimotopes as tools to unravel the evolution of the antibody landscape and the viral envelope escape which may provide us with new insights for vaccine design.</p> <p>Results</p> <p>This study led us to identify ITM4 plasma antibodies directed to the 4E10 epitope located in the gp41 membrane-proximal external region (MPER). Analysis of antibody specificities revealed unusual immunogenic properties of the ITM4 viral envelope, as not only the V3 loop and the gp41 MPER but also the C1 and lentivirus lytic peptide 2 (LLP2) region seem to be targets of the immune system. The 4E10-like antibodies are consistently elicited during the 6-year follow up period. HIV-1 ITM4 pseudoviruses showed an increasing resistance over time to MPER monoclonal antibodies 4E10 and 2F5, although no changes are found in the critical positions of the epitope. Neutralization of COT6.15 (subtype C; 4E10-sensitive) pseudoviruses with alanine substitutions in the MPER region indicated an overlapping specificity of the 4E10 monoclonal antibody and the ITM4 follow up plasma. Moreover the 4E10-like antibodies of ITM4 contribute to the BCN capacity of the plasma.</p> <p>Conclusions</p> <p>Using ITM4 BCN plasma and peptide phage display technology, we have identified a patient with 4E10-like BCN antibodies. Our results indicate that the elicited 4E10-like antibodies play a role in virus neutralization. The viral RNA was isolated at different time points and the ITM4 envelope sequence analysis of both early (4E10-sensitive) and late (4E10-resistant) viruses suggest that other regions in the envelope, outside the MPER region, contribute to the accessibility and sensitivity of the 4E10 epitope. Including ITM4 specific HIV-1 Env properties in vaccine strategies may be a promising approach.</p

The effects of dietary fibre type on satiety-related hormones and voluntary food intake in dogs

Depending on type and inclusion level, dietary fibre may increase and maintain satiety and postpone the onset of hunger. This 7-week study evaluated the effect of fibre fermentability on physiological satiety-related metabolites and voluntary food intake (VFI) in dogs. Sixteen healthy adult dogs were fed a low-fermentable fibre (LFF) diet containing 8·5% cellulose or a high-fermentable fibre (HFF) diet containing 8·5% sugarbeet pulp and 2% inulin. Large intestinal fibre degradation was evaluated by apparent faecal digestibility of nutrients and faecal SCFA and NH3 concentrations. Postprandial blood samples were obtained to determine postprandial plasma glucose, insulin, total peptide tyrosine–tyrosine (PYY), total glucagon-like peptide-1 (GLP-1) and total ghrelin concentrations. At the end of the study, the dogs were given a single meal of a dry dog food to determine VFI. Dogs fed the HFF diet had a significantly higher large intestinal fibre degradation and production of SCFA compared with the dogs fed the LFF diet. The HFF-fed dogs tended (P=0·058) to show a lower VFI at the end of the study. No treatment effects were found for postprandial plasma glucose, PYY, GLP-1 and ghrelin responses. The concentrations of these metabolites could not be related to the observed difference in VFI. The inclusion of fermentable fibre in canine diets may contribute to the prevention or mitigation of obesity through its effects on satiety. The underlying mechanisms require further investigation

Vertical variation in photosynthetic parameters in two different tropical forest ecosystems

Màster project submitted to obtain the degree of Master in Biology, specialisation Biodiversity: conservation and restoration. Universiteit Antwerpen. Faculty of Science. Department of Biology. Academic year 2015-2016Forests contribute to the carbon balance as the largest vegetative sink for atmospheric carbon (CO2). Anthropogenic emissions are counteracted by carbon sequestration in trees, but nutrients could be limiting photosynthesis and the effect could possibly be not as large as believed. In tropical forests, phosphorus (P) is only available from weathered bedrock and is thereby in an imbalance with the rising levels of carbon and nitrogen in the atmosphere. If P is limiting carbon uptake in tropical forests, global carbon cycle models are likely overestimating uptake by forests. Another overestimation might be to only conduct photosynthesis measurements on sunlit leaves of the canopy and take this as an overall canopy average, whilst a vertical profile in photosynthesis is very likely. Our study was conducted on two sites of the Amazonian rain forest in French Guiana. Photosynthesis and dark respiration (Rd) was measured of 120 trees in 12 plots per site. The plots were situated along a geographical gradient (at top, slope and bottom) to cover a large variety in soil P concentration. We derived the photosynthetic parameters Vcmax and Jmax from the photosynthesis measurements using the Farquhar model (Farquhar et al., 1980). The measurements were performed at two different height levels in the canopy to investigate the vertical profile. In this study we aimed to relate the spatial and vertical variability to parameters such as leaf P concentration, leaf height, light availability, the specific leaf area and the chlorophyll content (SPAD). Soil P concentrations were correlated with the leaf P concentrations, which indicates P uptake from the soil is limited. There were significant vertical differences in the leaves in Vcmax, Jmax, Rd and leaf P concentrations. We conclude that P limits the photosynthetic capacity in our study areas and vertical profiles of photosynthesis should be taken into account when estimating carbon uptake by a tropical forest ecosystem

Reduced capacity of antibodies from patients infected with human immunodeficiency virus type 1 (HIV-1) group O to neutralize primary isolates of HIV-1 group M viruses

Neutralizing antibody patterns in sera of persons infected with human immunodeficiency virus type 1 (HIV-1) groups M and a to their homologous and heterologous primary isolates were determined in a peripheral blood mononuclear cell-based neutralization assay and correlated with their ability to bind to V3 loop synthetic peptides. Most HIV-1 group M sera (9/16) neutralized HIV-1 group a viruses, whereas fewer group a sera (3/13) only weakly neutralized HIV-1 group M viruses. Group M sera neutralizing HIV-1 group a viruses neutralized other HIV-1 group M viruses with titers of 1:10-1:1280. V3 loop binding capacity of sera did not reflect their neutralizing capacity of the homologous isolate. Despite the reduced neutralizing capacity of group a-infected patients &apos; sera to group M viruses, some group M- infected patients &apos; sera neutralized both HIV-1 group M and a isolates, suggesting that they share some conserved neutralizing epitopes. Nucleic acid sequence analysis of the envelope gene of hu-man immunodeficiency virus type 1 (HIV-1) isolates has thus far distinguished at least 8 subtypes, A-H [1-3], which to-gether are referred to as HIV-1 group M (for major). However, the relevance of these genetic subtypes in terms of neutraliza

Increased Cardiac Myocyte PDE5 Levels in Human and Murine Pressure Overload Hypertrophy Contribute to Adverse LV Remodeling

Background: The intracellular second messenger cGMP protects the heart under pathological conditions. We examined expression of phosphodiesterase 5 (PDE5), an enzyme that hydrolyzes cGMP, in human and mouse hearts subjected to sustained left ventricular (LV) pressure overload. We also determined the role of cardiac myocyte-specific PDE5 expression in adverse LV remodeling in mice after transverse aortic constriction (TAC). Methodology/Principal Findings: In patients with severe aortic stenosis (AS) undergoing valve replacement, we detected greater myocardial PDE5 expression than in control hearts. We observed robust expression in scattered cardiac myocytes of those AS patients with higher LV filling pressures and BNP serum levels. Following TAC, we detected similar, focal PDE5 expression in cardiac myocytes of C57BL/6NTac mice exhibiting the most pronounced LV remodeling. To examine the effect of cell-specific PDE5 expression, we subjected transgenic mice with cardiac myocyte-specific PDE5 overexpression (PDE5-TG) to TAC. LV hypertrophy and fibrosis were similar as in WT, but PDE5-TG had increased cardiac dimensions, and decreased dP/dtmax and dP/dtmin with prolonged tau (P<0.05 for all). Greater cardiac dysfunction in PDE5-TG was associated with reduced myocardial cGMP and SERCA2 levels, and higher passive force in cardiac myocytes in vitro. Conclusions/Significance: Myocardial PDE5 expression is increased in the hearts of humans and mice with chronic pressure overload. Increased cardiac myocyte-specific PDE5 expression is a molecular hallmark in hypertrophic hearts with contractile failure, and represents an important therapeutic target