Degradation of crude oil in the rhizosphere of Sorghum bicolor

Dissipation of petroleum contaminants in the rhizosphere is likely the result of enhanced microbial degradation. Plant roots may encourage rhizosphere microbial activity through exudation of nutrients and by providing channels for increased water flow and gas diffusion. Phytoremediation of crude oil in soil was examined in this study using carefully selected plant species monitored over specific plant growth stages. Four sorghum (Sorghum bicolor L.) genotypes with differing root characteristics and levels of exudation were established in a sandy loam soil contaminated with 2700 mg crude oil/kg soil. Soils were sampled at three stages of plant growth: five leaf, flowering, and maturity. All vegetated treatments were associated with higher remediation efficiency, resulting in significantly lower total petroleum hydrocarbon concentrations than unvegetated controls. A relationship between root exudation and bioremediation efficiency was not apparent for these genotypes, although the presence of all sorghum genotypes resulted in significant removal of crude oil from the impacted soil.     

Plasma 3-nitrotyrosine and outcome in neonates with severe bronchopulmonary dysplasia after inhaled nitric oxide

Plasma protein levels of 3-nitrotyrosine and 3-chlorotyrosine were measured by LC-MS/MS at 0 and 72 h after the initiation of inhaled nitric oxide (INO) at 20 ppm in 22 prematurely born infants with clinically documented bronchopulmonary dysplasia. Infants were classified at the time of hospital discharge as either "off mechanical ventilation," "on mechanical ventilation," or "expired/organ failure." These outcomes were tested for association with changes in plasma levels of 3-nitrotyrosine and 3-chlorotyrosine and selected clinical risk factors. Infants whose 3-nitrotyrosine levels decreased over the 72 h period were more likely to wean off of mechanical ventilation (p =.03). There was no significant association between changes in 3-chlorotyrosne levels and outcome. After controlling for other variables, an odds ratio of 8.3 (95% CI: 1.3-54.4) for improved outcomes was observed if the 3-nitrotyrosine levels decreased. These data suggest that nitrative and oxidative stress may be related to the severity of lung disease and, consequentially, the overall outcome in this select group of infants with severe bronchopulmonary dysplasia.     

Acute G-CSF therapy is not protective during lethal E. coli sepsis

We investigated whether decreases in circulating polymorphonuclear neutrophils (PMN) during lethal Escherichia coli (E. coli) sepsis in canines are related to insufficient host granulocyte colony-stimulating factor (G-CSF). Two-year-old purpose-bred beagles had intraperitoneal E. coli-infected or -noninfected fibrin clots surgically placed. By 10 to 12 h following clot, both infected survivors and nonsurvivors had marked increases (P = 0.001) in serum G-CSF levels (mean peak G-CSF ng/ml +/- SE, 1,931 +/- 364 and 2,779 +/- 681, respectively) compared with noninfected controls (134 +/- 79), which decreased at 24 to 48 h. Despite increases in G-CSF, infected clot placement caused delayed (P = 0.06) increases in PMN (mean +/- SE change from baseline in cells x 10(3)/mm(3) at 24 and 48 h) in survivors (+3.9 +/- 3.9 and +13.8 +/- 3.6) compared with noninfected controls (+13.1 +/- 2.8 and +9.1 +/- 2.5). Furthermore, infected nonsurvivors had decreases in PMN (-1.4 +/- 1.0 and -1.1 +/- 2.3, P = 0.006 compared with the other groups). We next investigated whether administration of G-CSF immediately after clot placement and continued for 96 h to produce more rapid and prolonged high levels of G-CSF after infection would alter PMN levels. Although G-CSF caused large increases in PMN compared with control protein from 2 to 48 h following clot in noninfected controls, it caused much smaller increases in infected survivors and decreases in infected nonsurvivors (P = 0.03 for the ordered effect of G-CSF comparing the three groups). Thus insufficient host G-CSF is unlikely the cause of decreased circulating PMN in this canine model of sepsis. Other factors associated with sepsis either alone or in combination with G-CSF itself may reduce increases or cause decreases in circulating PMN.     

Partial saturation and regional variation in the blood-to-brain transport of leptin in normal weight mice

Impaired blood-brain barrier transport of leptin into the arcuate nucleus has been suggested to underlie obesity in humans and outbred aging mice. Here, we used a brain perfusion method in mice to measure transport rates and kinetic parameters for leptin at vascular concentrations between 0.15 and 130 ng/ml. Transport into whole brain was partially saturated at all concentrations, not only those seen in obesity. Leptin entered all regions of the brain, not only the hypothalamus, with entry and saturation rates differing among the brain regions. The value of the Michaelis-Menten constant of the transporter approximates normal serum levels and the maximum velocity value varies significantly among brain regions. These results suggest an important role for low serum levels signaling starvation status to the brain and show that the levels of leptin seen in obesity greatly saturate the transporter. Differences in regional uptake and saturation provide a mechanism by which leptin can control events mediated at the arcuate nucleus and other regions of the central nervous system with different regional thresholds for optimal function.     

Isolation, characterization, and chondrogenic potential of human bone marrow-derived multipotential stromal cells

Multipotential bone marrow stromal cells have the ability to differentiate along multiple connective tissue lineages including cartilage. In this study, we developed an efficient and reproducible procedure for the isolation of stromal cells from bone marrow aspirates of normal human donors based on the expression of endoglin, a type III receptor of the transforming growth factor-beta (TGF-beta) receptor family. We demonstrate that these cells have the ability of multiple lineage differentiation. Stromal cells represented 2-3% of the total mononuclear cells of the marrow. The cells displayed a fibroblastic colony formation in monolayer culture and maintained similar morphology with passage. Expression of cell surface molecules by flow cytometry displayed a stable phenotype with culture expansion. When cocultured with hematopoietic CD34(+) progenitor cells, stromal cells were able to maintain their ability to support hematopoiesis in vitro. Culture expanded stromal cells were placed in a 3-dimensional matrix of alginate beads and cultured in serum-free media in the presence of TGFbeta-3 for chondrogenic lineage progression. Increased expression of type II collagen messenger RNA was observed in the TGFbeta3 treated cultures. Immunohistochemistry performed on sections of alginate beads detected the presence of type II collagen protein. This isolation procedure for stromal cells and the establishment of the alginate culture system for chondrogenic progression will contribute to the understanding of chondrogenesis and cartilage repair.     

Impact of a red-shifted dye label for high throughput fluorescence polarization assays of G protein-coupled receptors

High throughput screening fluorescence polarization assays using G protein-coupled receptors (GPCRs) as targets have been compared using fluorescein and BODIPY TMR-labeled peptides. The red-shifted BODIPY TMR dye exhibits improved assay performance relative to fluorescein due to improvement in both ligand affinity to the GPCRs and assay precision brought about by the higher intensity probe. Furthermore, the red-shifted dye demonstrates an insensitivity to the effects of the highly colored compound tartrazine, which can produce false-negative results for assays conducted with fluorescein as a label.     

Leptin activation of mTOR pathway in intestinal epithelial cell triggers lipid droplet formation,cytokine production and increased cell proliferation

Accumulating evidence suggests that obesity and enhanced inflammatory reactions are predisposing conditions for developing colon cancer. Obesity is associated with high levels of circulating leptin. Leptin is an adipocytokine that is secreted by adipose tissue and modulates immune response and inflammation. Lipid droplets (LD) are organelles involved in lipid metabolism and production of inflammatory mediators, and increased numbers of LD were observed in human colon cancer. Leptin induces the formation of LD in macrophages in a PI3K/mTOR pathway-dependent manner. Moreover, the mTOR is a serine/threonine kinase that plays a key role in cellular growth and is frequently altered in tumors. We therefore investigated the role of leptin in the modulation of mTOR pathway and regulation of lipid metabolism and inflammatory phenotype in intestinal epithelial cells (IEC-6 cells). We show that leptin promotes a dose- and time-dependent enhancement of LD formation. The biogenesis of LD was accompanied by enhanced CXCL1/CINC-1, CCL2/MCP-1 and TGF-β production and increased COX-2 expression in these cells. We demonstrated that leptin-induced increased phosphorylation of STAT3 and AKT and a dose and time-dependent mTORC activation with enhanced phosphorilation of the downstream protein P70S6K protein. Pre-treatment with rapamycin significantly inhibited leptin effects in LD formation, COX-2 and TGF-β production in IEC-6 cells. Moreover, leptin was able to stimulate the proliferation of epithelial cells on a mTOR-dependent manner. We conclude that leptin regulates lipid metabolism, cytokine production and proliferation of intestinal cells through a mechanism largely dependent on activation of the mTOR pathway, thus suggesting that leptin-induced mTOR activation may contribute to the obesity-related enhanced susceptibility to colon carcinoma.     

Angelman syndrome-associated ubiquitin ligase UBE3A/E6AP mutants interfere with the proteolytic activity of the proteasome

Angelman syndrome, a severe neurodevelopmental disease, occurs primarily due to genetic defects, which cause lack of expression or mutations in the wild-type E6AP/UBE3A protein. A proportion of the Angelman syndrome patients bear UBE3A point mutations, which do not interfere with the expression of the full-length protein, however, these individuals still develop physiological conditions of the disease. Interestingly, most of these mutations are catalytically defective, thereby indicating the importance of UBE3A enzymatic activity role in the Angelman syndrome pathology. In this study, we show that Angelman syndrome-associated mutants interact strongly with the proteasome via the S5a proteasomal subunit, resulting in an overall inhibitory effect on the proteolytic activity of the proteasome. Our results suggest that mutated catalytically inactive forms of UBE3A may cause defects in overall proteasome function, which could have an important role in the Angelman syndrome pathology.Ubiquitination is a highly specific process that involves a group of proteins responsible for adding ubiquitin molecules to cellular substrates, thereby resulting in the modulation of numerous cellular pathways.¹ The deregulation of components of the ubiquitin conjugation system causes defects in many cellular functions and these have been associated with human pathogenesis.² Of the components involved in the ubiquitin cascade, the E3 ubiquitin ligases provide the substrate specificity. By attaching ubiquitin molecules to their substrates, E3 ligases have direct control over the functions and, in many cases, protein turnover of these substrates. In addition, loss of function in a number of E3 enzymes has been shown to have an important role in the development of severe physiological conditions such as certain cancers and neurological disorders.³ A representative instance of the latter is Angelman syndrome (AS), a severe neurodevelopmental disorder, with clinical features of mental retardation, developmental delay, ataxia and epilepsy.^{4, 5} The principal protein affected in AS is the E3 ubiquitin ligase E6-associated protein (E6AP/UBE3A), the gene being found on chromosome 15q11-13. UBE3A was initially identified as an interacting partner of high-risk HPV-16 and -18 E6 oncoproteins,^{6, 7} but was subsequently found to be linked to the development of AS. AS develops mainly due to genetic defects that lead to the loss of expression of the maternal allele of the UBE3A gene in the hypothalamus.^{8, 9} Between 65 and 75% of AS patients have been diagnosed with the deletions of 15q11-13, 3–7% of patients show uniparental disomy and ~3% of cases have been found with imprinting defects, such that the functionally defective maternal copy of the gene is expressed in the brain.⁵ In addition, there are also 5–11% of individuals with AS whose sequence analyses show UBE3A mutations. Most of these have in-frame deletions that would be predicted to result in protein truncations,^{10, 11} but a number of those patients have milder mutations, such as point mutations, that do not affect the expression of the full-length protein.^{12, 13} The majority of these mutations however are defective in ubiquitin ligase activity, indicating that the loss of enzymatic activity of UBE3A is important in promoting the development of AS.¹⁴Studies have demonstrated that ubiquitin ligase activity of UBE3A has a role in the proteasome-dependent degradation of several cellular substrates, and it can be reasoned that defects in the regulation of some of these substrates can contribute to AS development. However, although a number of UBE3A target proteins have been identified, including Sox9, C/EBPα, α-Synuclein, p27, promyelocytic leukemia (PML) tumor suppressor, annexin A1, amplified in breast cancer 1 (AIB1) and HHR23A,^{15, 16, 17, 18, 19, 20, 21, 22} characterization of their interactions with UBE3A have only partially contributed to an understanding of the molecular mechanisms behind the development of AS pathology. In addition, UBE3A has also been shown to interact with other components of the proteasome degradatory pathway, including the ubiquitin ligases HERC2, Ring1B and EDD,^{23, 24, 25} and recent studies demonstrated a direct interaction between UBE3A and the proteasome itself.^{26, 27} Whether any of these interactions might also be involved in AS development is an open question. Thus, although many proteins are known to be targeted by UBE3A for proteasomal degradation, much less is known about UBE3A interactions with the proteasome itself, or how these interactions might affect substrate turnover, or whether perturbations in this association can contribute to AS development.The 26S proteasome is a complex cellular machine that contains a 20S central core, a hollow tube composed of multiple proteasome subunits, which contain proteolytic sites. On each end of the 20S proteolytic core, there is an ATP-dependent 19S regulatory particle, which is involved in capturing the ubiquitinated proteins.²⁸ Among several subunits that are part of the 19S regulatory particle complex, there are two major ubiquitin receptors, Rpn10/S5a and Rpn13.^{29, 30, 31} The S5a subunit mediates the targeting of ubiquitin substrates to the proteasome by binding ubiquitin conjugates through a ubiquitin-interacting motif (UIM)³² and loss of this activity of S5a results in decreased proteolytic activity of the proteasome.^{33, 34, 35} It has also been shown that S5a is regulated by mono-ubiquitination, which inhibits its ability to interact with ubiquitin-conjugated substrates, and also leads to decreased proteasome activity.³¹ Recent studies have shown that UBE3A can directly ubiquitinate the S5a subunit, and that its Drosophila ortholog, Ube3a, mediates ubiquitination of the Drosophila S5a homolog, resulting in its subsequent degradation.^{26, 27} Structural studies have indicated that a number of AS-associated UBE3A point mutations occur in the HECT domain, which most likely lead to the expression of catalytically defective proteins.^{13, 14} We were therefore interested in investigating whether catalytically defective AS-associated point mutants can still interact with the S5a subunit and, furthermore, in determining whether they can exert any inhibitory effects on the proteasomal turnover of ubiquitinated substrates. We show here that AS-associated UBE3A mutants interact more strongly with S5a, with one of the consequences being a general inhibitory effect on the overall proteolytic activity of the proteasome. These results suggest that perturbation of overall proteasome function may be an important element in the development of AS, which thus shows many similarities with other proteasomal neurogical defects.     

Comparing plasma and faecal measures of steroid hormones in Adelie penguins Pygoscelis adeliae

Physiological measurements of both stress and sex hormones are often used to estimate the consequences of natural or human-induced change in ecological studies of various animals. Different methods of hormone measurement exist, potentially explaining variation in results across studies; methods should be cross-validated to ensure that they correlate. We directly compared faecal and plasma hormone measurements for the first time in a wild free-living species, the Adelie penguin (Pygoscelis adeliae). Blood and faecal samples were simultaneously collected from individual penguins for comparison and assayed for testosterone and corticosterone (or their metabolites). Sex differences and variability within each measure, and correlation of values across measures were compared. For both hormones, plasma samples showed greater variation than faecal samples. Males had higher mean corticosterone concentrations than females, but the difference was only statistically significant in faecal samples. Plasma testosterone, but not faecal testosterone, was significantly higher in males than females. Correlation between sample types was poor overall, and weaker in females than in males, perhaps because measures from plasma represent hormones that are both free and bound to globulins, whereas measures from faeces represent only the free portion. Faecal samples also represent a cumulative measure of hormones over time, as opposed to a plasma ‘snapshot’ concentration. Our data indicate that faecal sampling appears more suitable for assessing baseline hormone concentrations, whilst plasma sampling may best define immediate responses to environmental events. Consequently, future studies should ensure that they select the most appropriate matrix and method of hormone measurement to answer their research questions.