Unconjugated Bilirubin Restricts Oligodendrocyte Differentiation and Axonal Myelination

High levels of serum unconjugated bilirubin (UCB) in newborns are associated with axonal damage and glial reactivity that may contribute to subsequent neurologic injury and encephalopathy (kernicterus). Impairments in myelination and white matter damage were observed at autopsy in kernicteric infants. We have recently reported that UCB reduces oligodendrocyte progenitor cell (OPC) survival in a pure OPC in vitro proliferative culture. Here, we hypothesized that neonatal hyperbilirubinemia may also impair oligodendrocyte (OL) maturation and myelination. We used an experimental model of hyperbilirubinemia that has been shown to mimic the pathophysiological conditions leading to brain dysfunction by unbound (free) UCB. Using primary cultures of OL, we demonstrated that UCB delays cell differentiation by increasing the OPC number and reducing the number of mature OL. This finding was combined with a downregulation of Olig1 mRNA levels and upregulation of Olig2 mRNA levels. Addition of UCB, prior to or during differentiation, impaired OL morphological maturation, extension of processes and cell diameter. Both conditions reduced active guanosine triphosphate (GTP)-bound Rac1 fraction. In myelinating co-cultures of dorsal root ganglia neurons and OL, UCB treatment prior to the onset of myelination decreased oligodendroglial differentiation and the number of myelinating OL, also observed when UCB was added after the onset of myelination. In both circumstances, UCB decreased the number of myelin internodes per OL, as well as the myelin internode length. Our studies demonstrate that increased concentrations of UCB compromise myelinogenesis, thereby elucidating a potential deleterious consequence of elevated UCB.     

Computational study of conformational changes in human 3-hydroxy-3-methylglutaryl coenzyme reductase induced by substrate binding

Abstract

The enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is mainly involved in the regulation of cholesterol biosynthesis. HMGR catalyses the reduction of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) to mevalonate at the expense of two NADPH molecules in a two-step reversible reaction. In the present study, we constructed a model of human HMGR (hHMGR) to explore the conformational changes of HMGR in complex with HMG-CoA and NADPH. In addition, we analysed the complete sequence of the Flap domain using molecular dynamics (MD) simulations and principal component analysis (PCA). The simulations revealed that the Flap domain plays an important role in catalytic site activation and substrate binding. The apo form of hHMGR remained in an open state, while a substrate-induced closure of the Flap domain was observed for holo hHMGR. Our study also demonstrated that the phosphorylation of Ser872 induces significant conformational changes in the Flap domain that lead to a complete closure of the active site, suggesting three principal conformations for the first stage of hHMGR catalysis. Our results were consistent with previous proposed models for the catalytic mechanism of hHMGR.

Communicated by Ramaswamy H. Sarma     

Begin at the beginning: A BAC-end view of the passion fruit (Passiflora) genome

Background

The passion fruit (Passiflora edulis) is a tropical crop of economic importance both for juice production and consumption as fresh fruit. The juice is also used in concentrate blends that are consumed worldwide. However, very little is known about the genome of the species. Therefore, improving our understanding of passion fruit genomics is essential and to some degree a pre-requisite if its genetic resources are to be used more efficiently. In this study, we have constructed a large-insert BAC library and provided the first view on the structure and content of the passion fruit genome, using BAC-end sequence (BES) data as a major resource.

Results

The library consisted of 82,944 clones and its levels of organellar DNA were very low. The library represents six haploid genome equivalents, and the average insert size was 108 kb. To check its utility for gene isolation, successful macroarray screening experiments were carried out with probes complementary to eight Passiflora gene sequences available in public databases. BACs harbouring those genes were used in fluorescent in situ hybridizations and unique signals were detected for four BACs in three chromosomes (n = 9). Then, we explored 10,000 BES and we identified reads likely to contain repetitive mobile elements (19.6% of all BES), simple sequence repeats and putative proteins, and to estimate the GC content (~42%) of the reads. Around 9.6% of all BES were found to have high levels of similarity to plant genes and ontological terms were assigned to more than half of the sequences analysed (940). The vast majority of the top-hits made by our sequences were to Populus trichocarpa (24.8% of the total occurrences), Theobroma cacao (21.6%), Ricinus communis (14.3%), Vitis vinifera (6.5%) and Prunus persica (3.8%).

Conclusions

We generated the first large-insert library for a member of Passifloraceae. This BAC library provides a new resource for genetic and genomic studies, as well as it represents a valuable tool for future whole genome study. Remarkably, a number of BAC-end pair sequences could be mapped to intervals of the sequenced Arabidopsis thaliana, V. vinifera and P. trichocarpa chromosomes, and putative collinear microsyntenic regions were identified.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-816) contains supplementary material, which is available to authorized users.     

Floral divergence and temporal pollinator partitioning in two synchronopatric species of <Emphasis Type="Italic">Vigna</Emphasis> (Leguminosae-Papilionoideae)

Exclusivity of pollinators, temporal partitioning of shared pollinators and divergence in pollen placement on the shared pollinators’ bodies are mechanisms that prevent interspecific pollen flow and minimize competitive interactions in synchronopatric plant species. We investigated the floral biology, flower visitors, pollinator effectiveness and seasonal flower availability of two syntopic legume species of the genus Vigna, V. longifolia and V. luteola, in ‘restinga’ vegetation of an island in southern Brazil. Our goal was to identify the strategies that might mitigate negative consequences of their synchronous flowering. Vigna longifolia and V. luteola were self-compatible, but depended on pollinators to set seeds. Only medium to large bees were able to trigger the ‘brush type’ pollination mechanism. Vigna longifolia, with its asymmetrical corolla and hugging mechanism, showed a more restrictive pollination system, with precise sites of pollen deposition/removal on the bee’s body, compared to V. luteola, with its zygomorphic corolla and cymbiform keel. There was a daily temporal substitution in flower visitation by the main pollinators. Vigna longifolia and V. luteola had overlapping flowering phenology but the densities of their flowers fluctuated, resulting in a seasonal partitioning of flower visitation. The differences in corolla symmetry and mainly the temporal partitioning among pollinators throughout the day and the flowering season proved to be important factors in maintaining the synchronopatry of V. longifolia and V. luteola.     

PGC‐1α affects aging‐related changes in muscle and motor function by modulating specific exercise‐mediated changes in old mice

The age‐related impairment in muscle function results in a drastic decline in motor coordination and mobility in elderly individuals. Regular physical activity is the only efficient intervention to prevent and treat this age‐associated degeneration. However, the mechanisms that underlie the therapeutic effect of exercise in this context remain unclear. We assessed whether endurance exercise training in old age is sufficient to affect muscle and motor function. Moreover, as muscle peroxisome proliferator‐activated receptor γ coactivator 1α (PGC‐1α) is a key regulatory hub in endurance exercise adaptation with decreased expression in old muscle, we studied the involvement of PGC‐1α in the therapeutic effect of exercise in aging. Intriguingly, PGC‐1α muscle‐specific knockout and overexpression, respectively, precipitated and alleviated specific aspects of aging‐related deterioration of muscle function in old mice, while other muscle dysfunctions remained unchanged upon PGC‐1α modulation. Surprisingly, we discovered that muscle PGC‐1α was not only involved in improving muscle endurance and mitochondrial remodeling, but also phenocopied endurance exercise training in advanced age by contributing to maintaining balance and motor coordination in old animals. Our data therefore suggest that the benefits of exercise, even when performed at old age, extend beyond skeletal muscle and are at least in part mediated by PGC‐1α.     

Detection of Mycobacterium leprae DNA in clinical and environmental samples using serological analysis and PCR

Molecular Biology Reports - Leprosy is a chronic infectious disease caused by Mycobacterium leprae and persists as a serious public health problem in Brazil. This microorganism is inculturable,...     

Hypolipidemic and antiatherosclerotic potential of Pleurotus ostreatus, cultived by submerged fermentation in the high-fat diet fed rats

The ability of Pleurotus ostreatus biomass, cultived by submerged fermentation, to produce beneficial effect on lipid profile and macrophages activity during a high-fat diet (HFD) for a long-term intake was investigated. Blood samples were collected through cardiac puncture to measure the plasma cholesterol, triglycerides, low-density protein (LDL), high-density protein (HDL), aspartate aminotransferase (AST) activity, urea-blood urea nitrogen (BUN)/creatinine ratio of rats fed on an HFD for 4 months. Dosage of lipid hydroperoxides was carried out on methanolic extract of liver tissue. Peritoneal macrophages activity was evaluated in relation to the superoxide anion, hydrogen peroxide and nitric oxide production, phagocytosis and lysosomal volume. The administration of P. ostreatus significantly altered the lipid profile and oxidative stress as related to the LDL and triglycerides decrease and inhibitory effects on superoxide anion and hydrogen peroxide production. All findings of this study lead us to suggest that the P. ostreatus maybe a beneficial agent in the hyperlipidemia and atherosclerosis treatments.     

Secreted phosphatase activity induced by dimethyl sulfoxide in Herpetomonas samuelpessoai

The secreted form of mouse meprin A is a homooligomer of meprin alpha subunits that contain a prosequence, a catalytic domain, and three domains designated as MAM (meprin, A5 protein, receptor protein-tyrosine phosphatase mu), MATH (meprin and TRAF homology), and AM (AfterMath). Previous studies indicated that wild-type mouse meprin alpha is predominantly a secreted protein, while the MAM deletion mutant (DeltaMAM) is degraded intracellularly. The work herein indicates that the DeltaMAM mutant is ubiquitinated and degraded via the proteasomal pathway. Both wild-type meprin alpha and the DeltaMAM mutant interact with the molecular chaperones calnexin and calreticulin in the endoplasmic reticulum. The interactions of the chaperones with the DeltaMAM mutant were significantly prolonged in the presence of lactacystin, a specific inhibitor of the proteasome, whereas those with the wild type were not affected by this inhibitor. Trimming of the Asn-linked core oligosaccharides of meprin subunits was required for interactions with the chaperones. The data indicated that folding of the wild-type protein was accelerated by chaperones, whereas the rate of dimerization was unaffected. Thus, calnexin and calreticulin are intimately involved in the correct folding and transport of meprin to the plasma membrane, as well as in retrograde transport of the DeltaMAM mutant to the ubiquitin-dependent proteasomal degradative pathway in the cytosol.     

Deltamethrin-Mediated Toxicity and Cytomorphological Changes in the Midgut and Nervous System of the Mayfly Callibaetis radiatus

Immature instars of mayflies are important constituents of the food web in aquatic ecosystems (especially in Neotropical regions) and they are among the most susceptible arthropods to pyrethroid insecticides. These insecticides have been recognized as important stressors of freshwater ecosystems, but their cellular effects in aquatic insects have been neglected. Here, we assessed the susceptibility to deltamethrin (a typical type II pyrethroid) as well as the deltamethrin-mediated cytomorphological changes in the central nervous system and midgut of the mayfly Callibaetis radiatus. While the deltamethrin LC₅₀ for 24h of exposure was of 0.60 (0.46–0.78) μg of a.i/L, the survival of C. radiatus was significantly reduced in deltamethrin concentrations ≥ 0.25 μg a.i/L at 96h of exposure. Sub-lethal deltamethrin exposure severely affected the cytomorphology of C. radiatus midgut (e.g., muscle layer retraction, cytoplasm vacuolation, nucleus and striated border disorganization) and also induced slight cytomorphological changes in the brain (e.g., presence of pyknotic nuclei) and in the thoracic ganglia (e.g., vacuolation of neurons and presence of pyknotic nuclei) of these insects. However, DNA damage was absent in all of these organs, suggesting that the sublethal cellular stress induced by deltamethrin might disrupt physiological processes (e.g., metabolism or electrical signal transmission) rather than cause cell death (e.g., apoptosis) in C. radiatus. Thus, our findings indicated that deltamethrin actions at cellular levels represent a clear indication of sublethal effects on the C. radiatus survival abilities.     

Data-Limited Population-Status Evaluation of Two Coastal Fishes in Southern Angola Using Recreational Catch Length-Frequency Data

Excessive truncation of a population’s size structure is often identified as an important deleterious effect of exploitation, yet the effect on population persistence of size-structure truncation caused by exploitation is often not quantified due to data limitations. In this study, we estimate changes in eggs per recruit (EPR) using annual length-frequency samples over a 9 year period to assess persistence of the two most important recreational fishes in southern Angola: west coast dusky kob (Argyrosomus coronus) and leerfish (Lichia amia). Using a length- and age-structured model, we improve on an existing method to fit this type of model to length-frequency data and estimate EPR. The objectives of the methodological changes are to add flexibility and robustness to the approach for assessing population status in data-limited situations. Results indicate that dusky kob presents very low levels of EPR (5%-10% of the per recruit reproductive capacity in the absence of fishing) in 2013, whereas large inter-annual variability in leerfish estimates suggest caution must be applied when drawing conclusions about its exploitation status. Using simulated length frequency data with known parameter values, we demonstrate that recruitment decline due to overexploitation leads to overestimation of EPR values. Considering the low levels of EPR estimated for the study species, recruitment limitation is not impossible and true EPR values may be even lower than our estimates. It is, therefore, likely that management action, such as the creation of Marine Protected Areas, is needed to reconstitute the west coast dusky kob population.