Roles of Predicted Glycosyltransferases in the Biosynthesis of the Rhizobium etli CE3 O Antigen

The Rhizobium etli CE3 O antigen is a fixed-length heteropolymer. The genetic regions required for its synthesis have been identified, and the nucleotide sequences are known. The structure of the O antigen has been determined, but the roles of specific genes in synthesizing this structure are relatively unclear. Within the known O-antigen genetic clusters of this strain, nine open reading frames (ORFs) were found to contain a conserved glycosyltransferase domain. Each ORF was mutated, and the resulting mutant lipopolysaccharide (LPS) was analyzed. Tricine SDS-PAGE revealed stepwise truncations of the O antigen that were consistent with differences in mutant LPS sugar compositions and reactivity with O-antigen-specific monoclonal antibodies. Based on these results and current theories of O-antigen synthesis, specific roles were deduced for each of the nine glycosyltransferases, and a model for biosynthesis of the R. etli CE3 O antigen was proposed. In this model, O-antigen biosynthesis is initiated with the addition of N-acetyl-quinovosamine-phosphate (QuiNAc-P) to bactoprenol-phosphate by glycosyltransferase WreU. Glycosyltransferases WreG, WreE, WreS, and WreT would each act once to attach mannose, fucose, a second fucose, and 3-O-methyl-6-deoxytalose (3OMe6dTal), respectively. WreH would then catalyze the addition of methyl glucuronate (MeGlcA) to complete the first instance of the O-antigen repeat unit. Four subsequent repeats of this unit composed of fucose, 3OMe6dTal, and MeGlcA would be assembled by a cycle of reactions catalyzed by two additional glycosyltransferases, WreM and WreL, along with WreH. Finally, the O antigen would be capped by attachment of di- or tri-O-methylated fucose as catalyzed by glycosyltransferase WreB

\u3cem\u3eIn Vitro\u3c/em\u3e Biosynthesis and Chemical Identification of UDP-\u3cem\u3eN\u3c/em\u3e-acetyl-d-quinovosamine (UDP-d-QuiNAc)

N-acetyl-d-quinovosamine (2-acetamido-2,6-dideoxy-d-glucose, QuiNAc) occurs in the polysaccharide structures of many Gram-negative bacteria. In the biosynthesis of QuiNAc-containing polysaccharides, UDP-QuiNAc is the hypothetical donor of the QuiNAc residue. Biosynthesis of UDP-QuiNAc has been proposed to occur by 4,6-dehydration of UDP-N-acetyl-d-glucosamine (UDP-GlcNAc) to UDP-2-acetamido-2,6-dideoxy-d-xylo-4-hexulose followed by reduction of this 4-keto intermediate to UDP-QuiNAc. Several specific dehydratases are known to catalyze the first proposed step. A specific reductase for the last step has not been demonstrated in vitro, but previous mutant analysis suggested that Rhizobium etli gene wreQ might encode this reductase. Therefore, this gene was cloned and expressed in Escherichia coli, and the resulting His6-tagged WreQ protein was purified. It was tested for 4-reductase activity by adding it and NAD(P)H to reaction mixtures in which 4,6-dehydratase WbpM had acted on the precursor substrate UDP-GlcNAc. Thin layer chromatography of the nucleotide sugars in the mixture at various stages of the reaction showed that WbpM converted UDP-GlcNAc completely to what was shown to be its 4-keto-6-deoxy derivative by NMR and that addition of WreQ and NADH led to formation of a third compound. Combined gas chromatography-mass spectrometry analysis of acid hydrolysates of the final reaction mixture showed that a quinovosamine moiety had been synthesized after WreQ addition. The two-step reaction progress also was monitored in real time by NMR. The final UDP-sugar product after WreQ addition was purified and determined to be UDP-d-QuiNAc by one-dimensional and two-dimensional NMR experiments. These results confirmed that WreQ has UDP-2-acetamido-2,6-dideoxy-d-xylo-4-hexulose 4-reductase activity, completing a pathway for UDP-d-QuiNAc synthesis in vitro

The association of comorbidities, utilization and costs for patients identified with low back pain

BACKGROUND: Existing studies have examined the high prevalence of LBP along with the high treatment costs of patients with low back pain (LBP). Various factors have been shown to be correlated or predictive of chronic or episodic LBP including the characteristics of the initial episode, pain, comorbid conditions, psychosocial issues, and opiate use. This study replicates and extends earlier studies by examining the association of patient characteristics including baseline comorbidities with patterns of healthcare service use and cost. METHODS: This is a retrospective analysis of measures of comorbidities, healthcare use, and cost for patients identified with LBP, stratified by the number of LBP episodes. Administrative data associated with outpatient and hospital based care for the years 1996 through 2001, were used to identify adult patients with LBP. LBP patients continuously enrolled for 12 months prior and 24 months after their initial LBP event were included in the study. A LBP episode was identified as the number of 30-day periods where a patient had one or more healthcare events with a diagnosis consistent with LBP. Chi-square and multivariate regression analyses were employed to estimate the variation in utilization and costs. RESULTS: Of 16,567 patients enrolled, 67% were identified with only one LBP episode and 4.5% had ≥6. The prevalence of comorbidities, analgesic use, and healthcare service use, varied by the number of back pain episodes. Diabetes, rheumatoid arthritis, anxiety, psychotic illness, depression, use of opiates and NSAIDs were associated with significant incremental increases in costs (P < .003). CONCLUSION: Physical and mental health co-morbidities and measures of analgesic use were associated with chronicity, healthcare utilization and costs. Given the association of comorbidities and cost for patients with LBP, management approaches that are effective across chronic illnesses may prove to be beneficial for high cost patients identified with LBP

Exploring physical exposures and identifying high-risk work tasks within the floor layer trade

INTRODUCTION: Floor layers have high rates of musculoskeletal disorders yet few studies have examined their work exposures. This study used observational methods to describe physical exposures within floor laying tasks. METHODS: We analyzed 45 videos from 32 floor layers using Multimedia-Video Task Analysis software to determine the time in task, forces, postures, and repetitive hand movements for installation of four common flooring materials. We used the WISHA checklists to define exposure thresholds. RESULTS: Most workers (91%) met the caution threshold for one or more exposures. Workers showed high exposures in multiple body parts with variability in exposures across tasks and for different materials. Prolonged exposures were seen for kneeling, poor neck and low back postures, and intermittent but frequent hand grip forces. CONCLUSIONS: Floor layers experience prolonged awkward postures and high force physical exposures in multiple body parts, which probably contribute to their high rates of musculoskeletal disorders

Storytelling Morality: Ecofeminism, Agrarianism, and Pigs in the Field

Understanding our relationships with and obligations to the natural world through the labor and practice of food production is central to our development as moral beings and environmental citizens. Both ecofeminism and agrarianism—in their overlap and distance—can offer ideas about how best to express our environmental and citizenship ethics through the everyday act of growing, eating, and engaging with food. Raymond Anthony (2009) reminds us that a narrative ethics approach—embraced by both ecofeminism and agrarianism as a meaningful source of ethical wisdom—when applied to animal agriculture helps to build a more inclusive moral community. But Anthony cautions that the predominant agricultural storyline is made up of incompatible camps. He proposes a new story for agriculture, one that offers reconciliation or revitalization. In the spirit of this revitalization, we offer two stories of our material practice of raising pigs on an educational organic farm to illuminate what we see as important ethical, social, and environmental context for our new agricultural narrative. Through these stories we aim to give context to the theoretical ecofeminist and agrarian dialogue about ethics rooted in the land, so we might better understand what appropriate relationships with nonhuman others and natural systems might look like in practice

mRNA-mediated glycoengineering ameliorates deficient homing of human stem cell-derived hematopoietic progenitors

Generation of functional hematopoietic stem and progenitor cells (HSPCs) from human pluripotent stem cells (PSCs) has been a long-sought-after goal for use in hematopoietic cell production, disease modeling, and eventually transplantation medicine. Homing of HSPCs from bloodstream to bone marrow (BM) is an important aspect of HSPC biology that has remained unaddressed in efforts to derive functional HSPCs from human PSCs. We have therefore examined the BM homing properties of human induced pluripotent stem cell-derived HSPCs (hiPS-HSPCs). We found that they express molecular effectors of BM extravasation, such as the chemokine receptor CXCR4 and the integrin dimer VLA-4, but lack expression of E-selectin ligands that program HSPC trafficking to BM. To overcome this deficiency, we expressed human fucosyltransferase 6 using modified mRNA. Expression of fucosyltransferase 6 resulted in marked increases in levels of cell surface E-selectin ligands. The glycoengineered cells exhibited enhanced tethering and rolling interactions on E-selectin-bearing endothelium under flow conditions in vitro as well as increased BM trafficking and extravasation when transplanted into mice. However, glycoengineered hiPS-HSPCs did not engraft long-term, indicating that additional functional deficiencies exist in these cells. Our results suggest that strategies toward increasing E-selectin ligand expression could be applicable as part of a multifaceted approach to optimize the production of HSPCs from human PSCs