2,848 research outputs found
That Sheep May Safely Graze: Rebuilding Animal Health Care in War-Torn Afghanistan
The very mention of Afghanistan conjures images of war, international power politics, the opium trade, and widespread corruption. Yet the untold story of Afghanistanâs seemingly endless misfortune is the disruptive impact that prolonged conflict has had on ordinary rural Afghans, their culture, and the timeless relationship they share with their land and animals. In rural Afghanistan, when animals die, livelihoods are lost, families and communities suffer, and people may perish. That Sheep May Safely Graze details a determined effort, in the midst of war, to bring essential veterinary services to an agrarian society that depends day in and day out on the well-being and productivity of its animals, but which, because of decades of war and the disintegration of civil society, had no reliable access to even the most basic animal health care. The book describes how, in the face of many obstacles, a dedicated group of Afghan and expatriate veterinarians working for a small nongovernmental organization (NGO) in Kabul was able to create a national network of over 400 veterinary field units staffed by over 600 veterinary paraprofessionals. These paravets were selected by their own communities and then trained and outfitted by the NGO so that nearly every district in the country that needed basic veterinary services now has reliable access to such services. Most notably, over a decade after its inception and with Afghanistan still in free fall, this private sector, district-based animal health program remains vitally active. The community-based veterinary paraprofessionals continue to provide quality services to farmers and herders, protecting their animals from the ravages of disease and improving their livelihoods, despite the political upheavals and instability that continue to plague the country. The elements contributing to this sustainability and their application to programs for improved veterinary service delivery in developing countries beyond Afghanistan are described in the narrative.https://docs.lib.purdue.edu/purduepress_previews/1026/thumbnail.jp
Chemoenzymatic Synthesis of Cryptophycin Anticancer Agents by an Ester Bond-Forming Non-ribosomal Peptide Synthetase Module
Cryptophycins (Crp) are a group of cyanobacterial
depsipeptides with activity against drug-resistant tumors. Although they have been shown to be promising, further efforts are required to return these highly potent compounds to the clinic through a new generation of
analogues with improved medicinal properties. Herein,
we report a chemosynthetic route relying on themultifunctional enzyme CrpD-M2 that incorporates a 2-hydroxy acid moiety (unit D) into Crp analogues. CrpD-M2 is a unique nonribosomal peptide synthetase (NRPS) module comprised of condensation-adenylation-ketoreduction-thiolation (C-A-KR-T) domains. We interrogated A-domain 2-keto and 2-hydroxy acid activation and loading, and KR domain activity in the presence of NADPH and NADH. The
resulting 2-hydroxy acid was elongated with three synthetic
Crp chain elongation intermediate analogues through ester
bond formation catalyzed by CrpD-M2 C domain. Finally, the
enzyme-bound seco-Crp products were macrolactonized by
the Crp thioesterase. Analysis of these sequential steps was
enabled through LC-FTICR-MS of enzyme-bound intermediates
and products. This novel chemoenzymatic synthesis of
Crp involves four sequential catalytic steps leading to the
incorporation of a 2-hydroxy acid moiety in the final chain
elongation intermediate. The presented work constitutes the
first example where a NRPS-embedded KR domain is employed
for assembly of a fully elaborated natural product, and
serves as a proof-of-principle for chemoenzymatic synthesis of new Crp analogues
Image-based Quantification of 3D Morphology for Bifurcations in the Left Coronary Artery: Application to Stent Design
Background
Improved strategies for stentâbased treatment of coronary artery disease at bifurcations require a greater understanding of artery morphology. Objective
We developed a workflow to quantify morphology in the left main coronary (LMCA), left anterior descending (LAD), and left circumflex (LCX) artery bifurcations. Methods
Computational models of each bifurcation were created for 55 patients using computed tomography images in 3D segmentation software. Metrics including crossâsectional area, length, eccentricity, taper, curvature, planarity, branching law parameters, and bifurcation angles were assessed using openâsources software and custom applications. Geometric characterization was performed by comparison of means, correlation, and linear discriminant analysis (LDA). Results
Differences between metrics suggest dedicated or multistent approaches should be tailored for each bifurcation. For example, the side branch of the LCX (i.e., obtuse marginal; OM) was longer than that of the LMCA (i.e., LCXprox) and LAD (i.e., first diagonal; D1). Bifurcation metrics for some locations (e.g., LMCA Finet ratio) provide results and confidence intervals agreeing with prior findings, while revised metric values are presented for others (e.g., LAD and LCX). LDA revealed several metrics that differentiate between artery locations (e.g., LMCA vs. D1, LMCA vs. OM, LADprox vs. D1, and LCXprox vs. D1). Conclusions
These results provide a foundation for elucidating common parameters from healthy coronary arteries and could be leveraged in the future for treating diseased arteries. Collectively the current results may ultimately be used for design iterations that improve outcomes following implantation of future dedicated bifurcation stents
Studies on the Biosynthesis of the Stephacidin and Notoamide Natural Products: A Stereochemical and Genetic Conundrum
The stephacidin and notoamide natural products belong to a group of prenylated indole alkaloids containing a bicyclo[2.2.2]diazaoctane core. Biosynthetically, this bicyclic core is believed to be the product of an intermolecular DielsâAlder (IMDA) cycloaddition of an achiral azadiene. Since all of the natural products in this family have been isolated in enantiomerically pure form to date, it is believed that an elusive DielsâAlderase enzyme mediates the IMDA reaction. Adding further intrigue to this biosynthetic puzzle is the fact that several related Aspergillus fungi produce a number of metabolites with the opposite absolute configuration, implying that these fungi have evolved enantiomerically distinct DielsâAlderases. We have undertaken a program to identify every step in the biogenesis of the stephacidins and notoamides, and by combining the techniques of chemical synthesis and biochemical analysis we have been able to identify the two prenyltransferases involved in the early stages of the stephacidin and notoamide biosyntheses. This has allowed us to propose a modified biosynthesis for stephacidin A, and has brought us closer to our goal of finding evidence for, or against, the presence of a DielsâAlderase in this biosynthetic pathway.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83757/1/442_ftp.pd
Analysis of Diffusion of Ras2 in Saccharomyces cerevisiae Using Fluorescence Recovery after Photobleaching
Binding, lateral diffusion and exchange are fundamental dynamic processes
involved in protein association with cellular membranes. In this study, we
developed numerical simulations of lateral diffusion and exchange of
fluorophores in membranes with arbitrary bleach geometry and exchange of the
membrane localized fluorophore with the cytosol during Fluorescence Recovery
after Photobleaching (FRAP) experiments. The model simulations were used to
design FRAP experiments with varying bleach region sizes on plasma-membrane
localized wild type GFP-Ras2 with a dual lipid anchor and mutant GFP-Ras2C318S
with a single lipid anchor in live yeast cells to investigate diffusional
mobility and the presence of any exchange processes operating in the time scale
of our experiments. Model parameters estimated using data from FRAP experiments
with a 1 micron x 1 micron bleach region-of-interest (ROI) and a 0.5 micron x
0.5 micron bleach ROI showed that GFP-Ras2, single or dual lipid modified,
diffuses as single species with no evidence of exchange with a cytoplasmic
pool. This is the first report of Ras2 mobility in yeast plasma membrane. The
methods developed in this study are generally applicable for studying diffusion
and exchange of membrane associated fluorophores using FRAP on commercial
confocal laser scanning microscopes.Comment: Accepted for publication in Physical Biology (2010). 28 pages, 7
figures, 3 table
Identification and analysis of the bacterial endosymbiont specialized for production of the chemotherapeutic natural product ETâ743
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/115956/1/emi12908.pd
High Aldehyde Dehydrogenase Activity Identifies a Subset of Human Mesenchymal Stromal Cells with Vascular Regenerative Potential
During culture expansion, multipotent mesenchymal stromal cells (MSCs) differentially express aldehyde dehydrogenase (ALDH), an intracellular detoxification enzyme that protects long-lived cells against oxidative stress. Thus, MSC selection based on ALDH-activity may be used to reduce heterogeneity and distinguish MSC subsets with improved regenerative potency. After expansion of human bone marrow-derived MSCs, cell progeny was purified based on low versus high ALDH-activity (ALDHhi) by fluorescence-activated cell sorting, and each subset was compared for multipotent stromal and provascular regenerative functions. Both ALDHl° and ALDHhi MSC subsets demonstrated similar expression of stromal cell (\u3e95% CD73+, CD90+, CD105+) and pericyte (\u3e95% CD146+) surface markers and showed multipotent differentiation into bone, cartilage, and adipose cells in vitro. Conditioned media (CDM) generated by ALDHhi MSCs demonstrated a potent proliferative and prosurvival effect on human microvascular endothelial cells (HMVECs) under serum-free conditions and augmented HMVEC tube-forming capacity in growth factor-reduced matrices. After subcutaneous transplantation within directed in vivo angiogenesis assay implants into immunodeficient mice, ALDHhi MSC or CDM produced by ALDHhi MSC significantly augmented murine vascular cell recruitment and perfused vessel infiltration compared with ALDHl° MSC. Although both subsets demonstrated strikingly similar mRNA expression patterns, quantitative proteomic analyses performed on subset-specific CDM revealed the ALDHhi MSC subset uniquely secreted multiple proangiogenic cytokines (vascular endothelial growth factor beta, platelet derived growth factor alpha, and angiogenin) and actively produced multiple factors with chemoattractant (transforming growth factor-ÎČ, C-X-C motif chemokine ligand 1, 2, and 3 (GRO), C-C motif chemokine ligand 5 (RANTES), monocyte chemotactic protein 1 (MCP-1), interleukin [IL]-6, IL-8) and matrix-modifying functions (tissue inhibitor of metalloprotinase 1 & 2 (TIMP1/2)). Collectively, MSCs selected for ALDHhi demonstrated enhanced proangiogenic secretory functions and represent a purified MSC subset amenable for vascular regenerative applications. Stem Cells 2017;35:1542â1553
The ACS Virgo Cluster Survey IV: Data Reduction Procedures for Surface Brightness Fluctuation Measurements with the Advanced Camera for Surveys
The Advanced Camera for Surveys (ACS) Virgo Cluster Survey is a large program
to image 100 early-type Virgo galaxies using the F475W and F850LP bandpasses of
the Wide Field Channel of the ACS instrument on the Hubble Space Telescope
(HST). The scientific goals of this survey include an exploration of the
three-dimensional structure of the Virgo Cluster and a critical examination of
the usefulness of the globular cluster luminosity function as a distance
indicator. Both of these issues require accurate distances for the full sample
of 100 program galaxies. In this paper, we describe our data reduction
procedures and examine the feasibility of accurate distance measurements using
the method of surface brightness fluctuations (SBF) applied to the ACS Virgo
Cluster Survey F850LP imaging. The ACS exhibits significant geometrical
distortions due to its off-axis location in the HST focal plane; correcting for
these distortions by resampling the pixel values onto an undistorted frame
results in pixel correlations that depend on the nature of the interpolation
kernel used for the resampling. This poses a major challenge for the SBF
technique, which normally assumes a flat power spectrum for the noise. We
investigate a number of different interpolation kernels and show through an
analysis of simulated galaxy images having realistic noise properties that it
is possible, depending on the kernel, to measure SBF distances using
distortion-corrected ACS images without introducing significant additional
error from the resampling. We conclude by showing examples of real image power
spectra from our survey.Comment: ApJS, in press, complete version of the paper at the link:
http://www.physics.rutgers.edu/~pcote/acs/publications.htm
Automated genome mining for natural products
Abstract
Background
Discovery of new medicinal agents from natural sources has largely been an adventitious process based on screening of plant and microbial extracts combined with bioassay-guided identification and natural product structure elucidation. Increasingly rapid and more cost-effective genome sequencing technologies coupled with advanced computational power have converged to transform this trend toward a more rational and predictive pursuit.
Results
We have developed a rapid method of scanning genome sequences for multiple polyketide, nonribosomal peptide, and mixed combination natural products with output in a text format that can be readily converted to two and three dimensional structures using conventional software. Our open-source and web-based program can assemble various small molecules composed of twenty standard amino acids and twenty two other chain-elongation intermediates used in nonribosomal peptide systems, and four acyl-CoA extender units incorporated into polyketides by reading a hidden Markov model of DNA. This process evaluates and selects the substrate specificities along the assembly line of nonribosomal synthetases and modular polyketide synthases.
Conclusion
Using this approach we have predicted the structures of natural products from a diverse range of bacteria based on a limited number of signature sequences. In accelerating direct DNA to metabolomic analysis, this method bridges the interface between chemists and biologists and enables rapid scanning for compounds with potential therapeutic value.http://deepblue.lib.umich.edu/bitstream/2027.42/112362/1/12859_2008_Article_2915.pd
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