In JoVE (1)

Other Publications (41)

Articles by Pravin Chordia in JoVE

 JoVE Engineering

Bringing the Visible Universe into Focus with Robo-AO

1Caltech Optical Observatories, California Institute of Technology, 2Department of Astronomy, California Institute of Technology, 3Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 4Inter-University Centre for Astronomy & Astrophysics, 5Observatories of the Carnegie Institution for Science, 6Benoziyo Center for Astrophysics, Weizmann Institute of Science

Other articles by Pravin Chordia on PubMed

Ureteral and Vesical Metastases from Parenchymal Renal Carcinoma: Case Report and Review of Literature

The Journal of Urology. Sep, 1969  |  Pubmed ID: 5808881

Premature Rupture of the Membranes Before 38 Weeks of Pregnancy

The British Journal of Clinical Practice. Sep, 1978  |  Pubmed ID: 737117

Ultrastructural Observations in an Alcoholic Patient with Post-surgical Pseudomonas Infection

Annals of Clinical and Laboratory Science. Mar-Apr, 1981  |  Pubmed ID: 7259089

Gram negative bacteria were seen in the peripheral blood and within the neutrophils of a patient with bacteremic shock secondary to Pseudomonas aeruginosa infection. By electron microscopy, bacteria were present either in vacuoles or in the cytoplasm of neutrophils. When seen in the cytoplasm, they were surrounded by amorphous material which most probably represented fused lysosomal granules. In both cases, the microorganisms appeared morphologically normal. The presumption is that there was a pre-existing defect of neutrophilic lysosomal formation or function. These findings indicate the importance of studying neutrophil morphology and function in patients with persistent infections.

Serum Creatine Phosphokinase (CPK) Isoenzymes in Perinatal Asphyxia

Indian Journal of Pediatrics. Sep-Oct, 1982  |  Pubmed ID: 7188200

Metrifonate in the Treatment of Schistosoma Haematobium Infection

New York State Journal of Medicine. Oct-Nov, 1983  |  Pubmed ID: 6580560

Hepatic Complications of Bone Marrow Transplant

Indian Journal of Gastroenterology : Official Journal of the Indian Society of Gastroenterology. Apr, 1987  |  Pubmed ID: 3294584

Amantadine for Treatment of Cocaine Dependence in Methadone-maintained Patients

The American Journal of Psychiatry. Apr, 1988  |  Pubmed ID: 3348463

Management of a Bleeding Aberrant Cervical Artery Following Vacuum Suction Termination. Case Report

British Journal of Obstetrics and Gynaecology. Apr, 1988  |  Pubmed ID: 3382617

Interaction of a Fluorescent Derivative of Paclitaxel (Taxol) with Microtubules and Tubulin-colchicine

Biochemistry. Nov, 1996  |  Pubmed ID: 8916903

A fluorescent derivative of paclitaxel, 2-debenzoyl-2-(m-aminobenzoyl)paclitaxel (2-AB-PT), has been prepared. 2-AB-PT induces microtubule assembly in vitro, but is about 3-fold less potent than paclitaxel itself. The absorption and emission characteristics of 2-AB-PT were analyzed as a function of solvent. It was found that both spectra were perturbed by specific solvent effects when the solvent contained a hydrogen bond donor. The absorption and fluorescence spectra of 2-AB-PT bound to microtubules could not be mimicked by a single solvent, but the absorption and emission maxima of the tubulin-bound species could be duplicated by a solvent mixture of DMSO and water. These results indicate that the fluorophore binding site on the microtubule is in an environment of intermediate polarity that is accessible to a hydrogen bond donor in the vicinity of the m-amino group. In addition, tubulin fluorescence is quenched in the 2-AB-PT/microtubule complex, and energy transfer from tubulin to 2-AB-PT is apparent. These results indicate that substituents on the C-2 position of paclitaxel associate with tubulin when bound to the microtubule. 2-AB-PT binding to microtubules was quantitatively analyzed by fluorescence titrations. Two classes of binding sites for 2-AB-PT on microtubules were found. The high affinity site has an apparent association constant (K1app) of 2.0 (+/- 0.9) x 10(7) M-1 and an apparent binding stoichiometry (n1app) of 0.8 (+/- 0.1) sites/tubulin dimer in the microtubule. The apparent association constant for the lower affinity site is about 100-fold less than that of the higher affinity site (K2app = 2.1 (+/- 0.7) x 10(5) M-1), and the stoichiometry of the lower affinity site or class of sites (n2app) was found to be 1.3 +/- 0.1. Paclitaxel blocked 2-AB-PT binding to the high affinity site. No binding of 2-AB-PT to unassembled tubulin was observed, but the emission spectrum of 2-AB-PT in the presence of the tubulin-colchicine complex resembled the emission spectrum of the ligand bound to microtubules. It was previously shown that paclitaxel can induce GTPase activity in the tubulin-colchicine complex, indicating that paclitaxel can bind to unassembled tubulin in its complex with colchicine [Carlier, M.-F., & Pantaloni, D. (1983) Biochemistry 22, 4814-4822]. Rigorous characterization of the aggregation state of the protein under these conditions demonstrates that 2-AB-PT is also capable of binding to the tubulin-colchicine complex.

Synthesis and Biological Evaluation of 2-epi-Paclitaxel

The Journal of Organic Chemistry. Jan, 1996  |  Pubmed ID: 11667011

Molecular Mobility of Nitroxyl-labelled Taxol During Tubulin Assembly

FEBS Letters. Mar, 1997  |  Pubmed ID: 9094427

Taxol is an important natural anticancer agent that binds to beta-tubulin and suppresses microtubule depolymerization. We have used electron paramagnetic resonance (EPR) spectroscopy to analyze the molecular motion of three novel nitroxyl free radical taxol analogues. Taxol was chemically modified at C2 or C7 carbon of the taxane ring with the TEMPO free radical to yield two spin-labelled taxols and concurrently at C2' and 3'N of the side chain to yield a spin-labelled taxol biradical. Nitroxyl moieties attached to the taxane ring are significantly restricted in their molecular motion during microtubule assembly, and they show no molecular restriction upon binding to tubulin. We conclude that taxol binds to tubulin in a way such that the taxane ring is not constrained by the dimer structure. However, the taxane ring is strongly immobilized after polymerization of tubulin, i.e. it is incorporated into the structure of microtubule. In contrast, the nitroxy moieties of the taxol biradical show strong immobilization upon attachment to tubulin. The nitroxyl energy exchange is restricted prior to the assembly of microtubules, and no differences associated with the process of polymerization were detected. The taxol side chain resides in a region that is not significantly constrained during polymerization.

Synthesis and Biological Activity of A-nor-paclitaxel Analogues

Bioorganic & Medicinal Chemistry. May, 1997  |  Pubmed ID: 9208103

A number of paclitaxel analogues with a 5-membered A-ring (A-nor-paclitaxels, or (15-->1)-abeo-paclitaxels) have been prepared in order to determine whether analogues of this class might have improved bioactivity as compared with paclitaxel. Most of the compounds synthesized were less active than paclitaxel, but one analogue was equivalent to paclitaxel in a tubulin-assembly assay, and another analogue was more cytotoxic than paclitaxel in two different cell lines of the NCI screen.

Identification of the Structural Region of Taxol That May Be Responsible for Cytokine Gene Induction and Cytotoxicity in Human Ovarian Cancer Cells

Cancer Chemotherapy and Pharmacology. 1998  |  Pubmed ID: 9523735

Interleukin-8 (IL-8) is a pleiotropic chemokine with both chemoattractant and angiogenic properties. In addition to its cytotoxic effects on ovarian cancer cells, taxol can transcriptionally activate genes such as IL-8 that may play a role in tumorigenesis. Utilizing IL-8 as a prototypic marker of tumor-derived modulators of growth, we undertook a systematic study of taxol and 11 structurally modified taxol analogs to identify the region of the taxane skeleton responsible for IL-8 gene induction.

Distances Between the Paclitaxel, Colchicine, and Exchangeable GTP Binding Sites on Tubulin

Biochemistry. May, 1998  |  Pubmed ID: 9578547

Distances between the paclitaxel, colchicine, and exchangeable GTP binding sites on tubulin polymers have been probed using fluorescence spectroscopy. Techniques for measuring fluorescence resonance energy transfer (FRET) between fluorescent or chromophoric ligands for each binding site were employed. 2-Debenzoyl-2-(m-aminobenzoyl)paclitaxel (2-AB-PT) was the fluorophore ligand for the paclitaxel binding site; thiocolchicine, allocolchicine, and MDL 27048 were probes for the colchicine site, and 2'(or 3')-O-(trinitrophenyl)guanosine 5'-triphosphate (TNP-GTP) was the fluorophore ligand for the exchangeable GTP site. The distance between the colchicine and paclitaxel binding sites was determined with two different acceptor ligands in the colchicine site. An average distance distribution of 17 A was found in both cases. Energy transfer between 2-AB-PT bound to the paclitaxel site and TNP-GTP (acceptor) bound to the exchangeable GTP site was observed in the polymer. The average distance distribution between the fluorophores was 16.0 A, but the half-width of the distribution was large (17.9 A), which indicates that energy transfer between more than one donor-acceptor pair occurred in the system. One interpretation of this result is that 2-AB-PT serves as an energy transfer donor for two GTP sites, one contained on the same subunit and one on an adjacent protofilament. No FRET was observed between ligands bound to the colchicine and exchangeable GTP sites, indicating that the result of colchicine binding on the GTP region of beta-tubulin is a long range, allosteric effect. The results from these experiments are interpreted in terms of known structural features of microtubules.

Synthesis and Biological Evaluation of 2-acyl Analogues of Paclitaxel (Taxol)

Journal of Medicinal Chemistry. Sep, 1998  |  Pubmed ID: 9733497

The anticancer drug paclitaxel (Taxol) has been converted to a large number of 2-debenzoyl-2-aroyl derivatives by three different methods. The bioactivities of the resulting analogues were determined in both tubulin polymerization and cytotoxicity assays, and several analogues with enhanced activity as compared with paclitaxel were discovered. Correlation of cytotoxicity in three cell lines with tubulin polymerization activity showed reasonable agreement. Among the cell lines examined, the closest correlation with antitubulin activity was observed with a human ovarian carcinoma cell line.

Synthesis and Biological Evaluation of 1-Deoxypaclitaxel Analogues

The Journal of Organic Chemistry. Mar, 1999  |  Pubmed ID: 11674269

The naturally occurring taxoid baccatin VI has been converted to various 1-deoxypaclitaxel derivatives by selective deacylation followed by attachment of the C-13 side chain. The bioactivities of the resulting analogues were determined in both tubulin polymerization and cytotoxicity assays, and several analogues with activity comparable to that of paclitaxel were discovered. It thus appears that the 1-hydroxyl group is not necessary for the activity of paclitaxel.

Synthesis and Bioactivity of 2,4-diacyl Analogues of Paclitaxel

Bioorganic & Medicinal Chemistry. Jan, 2001  |  Pubmed ID: 11197337

The 2,4-diacyl paclitaxel analogues 8a-8r were prepared from paclitaxel by acylation of 4-deacetyl-2-debenzoylpaclitaxel 1,2-carbonate (3) followed either by hydrolysis of the carbonate and acylation or by direct treatment of the carbonate with an aryllithium. Some of the resulting derivatives showed significantly improved tubulin assembly activity and cytotoxicity as compared with paclitaxel; in some cases this improvement was especially significant for paclitaxel-resistant cell lines.

A Facile Diels-Alder Reaction with Benzene: Synthesis of the Bicyclo[2.2.2]octene Skeleton Promoted by Rhenium

Journal of the American Chemical Society. Oct, 2001  |  Pubmed ID: 11674016

2-Aminothiazoles: a New Class of Agonist Allosteric Enhancers of A(1) Adenosine Receptors

Bioorganic & Medicinal Chemistry Letters. Jun, 2002  |  Pubmed ID: 12039562

This report describes the synthesis and structure-activity relationships of a new class of A(1) adenosine receptor agonist allosteric enhancers, 2-aminothiazolium salts. The EC(50) of compounds 6a, 6b, 7, and 8 were 0.3, 4.5, 3.8, and 1.2 microM, substantially lower than that of the 'Gold Standard' 2-amino-3-benzoyl thiophene (PD 81,723), which has an EC(50) of 38 microM.

In Vitro Metabolism of 2-acetylbenzothiophene: Relevance to Zileuton Hepatotoxicity

Chemical Research in Toxicology. Feb, 2004  |  Pubmed ID: 14967000

Zileuton, an inhibitor of 5-lipooxygenase, the initial enzyme in the leukotriene pathway, was marketed as a new treatment for asthma. This drug has been associated with liver toxicity, which has limited its clinical usefulness. We provide evidence here that the liver toxicity likely involves a sequence of biotransformations leading to 2-acetylbenzothiophene (2-ABT), which is subsequently metabolized to give a reactive intermediate(s). In vitro experiments with the human lymphoblast MCL5 cell line demonstrated that 2-ABT is cytotoxic in a P450-dependent manner. Human liver microsome (HLM) incubations with 2-ABT revealed the formation of two short-lived oxidized species, "M + 16" and "M + 32". Both of these metabolites formed adducts in the presence of GSH or NAC. Singly oxidized M + 16 adducts, from either GSH or NAC, appeared to be unstable in acidic medium and eliminated water readily to form a new compound. Authentic synthetic standards demonstrated that 2-ABT-S-oxide M1 corresponded to the M + 16 metabolite and that the S-oxide underwent nucleophilic addition with GSH and NAC to produce the singly oxidized adducts observed in HLM. The S-oxide adducts readily eliminated water to form a rearomatized 2-ABT-GSH adduct or 2-ABT-NAC adduct. Coelution experiments with the synthetic standard confirmed the structure of the eliminated 2-ABT-NAC adduct C1. LC/MS analyses of urine samples collected from rats dosed with zileuton indicate that C1 is a metabolite of zileuton formed in vivo. The in vitro and in vivo data presented here demonstrate the formation of 2-ABT from zileuton and its further bioactivation to a potentially toxic metabolite.

Regioselective Oxidation of 2-amino-3-aroyl-4,5-dialkylthiophenes by DMSO

Bioorganic & Medicinal Chemistry Letters. Feb, 2004  |  Pubmed ID: 15012996

Solutions of 2-amino-3-aroyl-4,5-dialkylthiophenes in DMSO (dimethyl sulfoxide) undergo regioselective oxidation of benzylic carbon under mild conditions. We describe three examples and propose a mechanism for oxidation.

Transition Metal-stabilized Arenium Cations: Protonation of Arenes Dihapto-coordinated to Pi-basic Metal Fragments

Journal of the American Chemical Society. Jun, 2004  |  Pubmed ID: 15161309

A series of metal complexes was synthesized in which arenes were dihapto-coordinated to pi-basic metal fragments having the general form [TpM(pi-acid)(L)], where Tp = hydridotris(pyrazolyl)borate, M = rhenium, molybdenum, or tungsten, pi-acid = CO or NO(+), and L = 1-methylimidazole, 1-butylimidazole, pyridine, or trimethylphosphine. The arene complexes were shown to be significantly more basic than the analogous pentaammineosmium(II) arene complexes and were protonated by moderate acids to give remarkably stable eta(2) and eta(3) arenium cation complexes. A crystal structure of [TpRe(CO)(MeIm)(5,6-eta(2)-2H-anisolium)](OTf) confirmed the eta(2) coordination of the anisolium ligand, but suggests a weak long-range interaction between the metal and C1 of the anisolium.

Michael Addition Reactions with Eta2-coordinated Anisoles: Controlling the Stereochemistry of the Para and Benzylic Carbons

Journal of the American Chemical Society. Dec, 2004  |  Pubmed ID: 15563183

Several eta(2)-coordinated anisole complexes were treated with various Michael acceptors in the presence of a Lewis or Bronsted acid to generate stable 4H-anisolium complexes. These reactions were found to proceed with high stereochemical control with predictable outcomes, provided that the moderate acid (NH(2)Ph(2))OTf was used and the complex was dissolved in an acidic solution. The stereochemistry is shown to originate from an unexpectedly high preference for one coordination diastereomer of the anisole complex in the solid state and a Diels-Alder like transition state for the Michael reaction.

6-aryl-8H-indeno[1,2-d]thiazol-2-ylamines: A1 Adenosine Receptor Agonist Allosteric Enhancers Having Improved Potency

Journal of Medicinal Chemistry. Aug, 2005  |  Pubmed ID: 16078833

Allosteric enhancers (AEs) of the A(1) adenosine receptor (A(1)AR) have potential as drugs for treating neurological, cardiovascular, and renal diseases. This report describes the synthesis and evaluation of a series of 6-aryl-8H-indeno[1,2-d]thiazol-2-ylamines that exhibited AE activity at the A(1)AR. Palladium-mediated condensation of arylboronic acids with 5-bromoindan-1-one generated arylindanones 2a-aj for iodine-catalyzed condensation with thiourea, generating 2-aminothiazolium salts 3a-aj. Binding studies using membranes from cells stably expressing human A(1)ARs, A(2A)ARs, or A(3)ARs evaluated AE activity and receptor subtype selectivity. The EC(50) of the AE activities of compounds 3m-o, 3x, and 3ae were 2.2, 1.5, 0.9, 1.0, and 3.0 muM, respectively, substantially lower than that of the well characterized 2-amino-3-aroylthiophene (PD 81,723), >10 microM. The new compounds also have substantially higher maximal AE activity. These compounds had no AE activity at the A(2A)AR and only minimal activity at the A(3)AR.

Probiotic Amelioration of Azotemia in 5/6th Nephrectomized Sprague-Dawley Rats

TheScientificWorldJournal. Aug, 2005  |  Pubmed ID: 16127597

The present study was to test the hypothesis that, selected bacteria instilled into the gastrointestinal tract could help in converting nitrogenous wastes accumulated due to renal insufficiency into non-toxic compounds; thereby, ameliorating the biochemical imbalance. Herein we describe a prospective, blinded, placebo controlled pilot-study, using 5/6th nephrectomized Sprague Dawley rat, as a chronic renal failure model. The study group consisted of 36 nephrectomized and 7 non-nephrectomized (control) rats. After two-week nephrectomy stabilization, cohorts of six nephrectomized rats were fed casein-based diet plus one of the following regimens: (A) Control, (B) Placebo (casein-based diet without probiotics), (C) Bacillus pasteurii, (D) Sporolac(R), (E) Kibow cocktail, (F) CHR Hansen Cocktail, and (G) ECONORM. Subsequently, blood (retro-orbital) and urine (collected for measurements of blood urea-nitrogen and creatinine respectively), body weight and bacterial counts (feces) were obtained at regular intervals. The study end-points were to determine if any of the probiotic dietary supplements facilitated, (1) decreased blood concentrations of uremic toxins, (2) altered renal function, and (3) prolonged survival. After 16 weeks of treatment, regimens C and D significantly prolonged the life span of uremic rats, in addition to showing a reduction in blood urea-nitrogen levels, concluding that supplementation of probiotic formulation to uremic rats slows the progression of azotemia, which may correlate with prolonged life span of uremic rats. Derivative trials of probiotic treatment of larger animals and humans will further assess the potential role of probiotic formulations in delaying the onset and clinical severity of clinical illness at different stages of renal failure.

Irreversible Alkylation of Human Serum Albumin by Zileuton Metabolite 2-acetylbenzothiophene-S-oxide: a Potential Model for Hepatotoxicity

Chemical Research in Toxicology. Dec, 2007  |  Pubmed ID: 17944539

2-acetylbenzothiophene-S-oxide (2-ABT-S-oxide or M1) is a reactive metabolite of zileuton, a drug used in the treatment of asthma and is capable of conjugating with glutathione in vitro. Human serum albumin (HSA) is the most abundant protein in plasma and plays a critical role in detoxifying reactive oxygen species. The current research is focused on understanding the interaction between M1 and HSA. The stability studies revealed the half-life of M1 to be about 0.85 h in HSA, 1.82 h in human plasma, and 4.48 h in phosphate-buffered saline (PBS) as determined by first-order approximation. The alkylation rate constant k for HSA was 20 M(-1) min(-1). After quenching with acetonitrile, the half-life of M1 did not change significantly, indicating that M1 is covalently bound to HSA. LC-MS and LC-MS/MS analysis of human plasma revealed the M1 alkylated peptide P (m/z 870) formed by HSA conjugation and concomitant water elimination. The specific amino acid on HSA bound to M1 was identified as Cys-34. This alkylation is observed to be concentration- and incubation-time-dependent in human plasma. HSA oxidized by N, N'-diacetyl-L-cystine exhibits a compromised ability of HSA to react with M1. The alkylated HSA diminished the binding affinity for warfarin. Furthermore, the alkylation was found to be irreversible in the dialysis experiment. In addition, M1 decomposes to 2-ABT in the presence of HSA, presumably acting as an oxidant. The formation of 2-ABT in the incubation and the self-condensation of M1 in PBS indicate that the alkylation of Cys-34 is only one of a number of reactions that occur in the presence of HSA. Irreversible protein modification may potentially lead to a loss of its function. HSA irreversible alkylation represents a model for other proteins to be potentially toxic and thus may help explain zileuton hepatotoxicity.

In Vitro Nimesulide Studies Toward Understanding Idiosyncratic Hepatotoxicity: Diiminoquinone Formation and Conjugation

Chemical Research in Toxicology. Jan, 2009  |  Pubmed ID: 19053182

Nimesulide is a nonsteroidal anti-inflammatory drug (NSAID) marketed in more than 50 countries. This drug has caused rare and idiosyncratic but severe hepatotoxicity. The mechanisms associated with and factors responsible for this toxicity remain unknown. One of the nimesulide metabolites identified in human urine is 4-amino-2-phenoxy-methanesulfonanilide (M1). In the current study, we demonstrate that M1 is a stable metabolite that is highly susceptible to facile oxidation by cytochrome P450 enzymes (P450s) to form a reactive diiminoquinone intermediate (M2). Direct detection of M2 was difficult by LC-MS. However, its formation was confirmed indirectly by identification of N-acetyl-cysteine (NAC) adducts of M2. The formation of diiminoquinone M2 was P450 mediated with 2C19 and 1A2 as the two principal P450 enzymes catalyzing M1 oxidation. M1 metabolism irreversibly inhibited 2C19 but activated 1A2 in a time-dependent manner. P450 2C19 exclusively mediated further metabolism of M1 to the amino hydroxynimesulide M3 and its diiminoquinone M4. Similar to M2, M4 is also reactive and can be observed indirectly as its NAC adduct. Nucleophilic addition to diiminoquinone M2 occurs with low regioselectivity, yielding three adducts (the peak area ratio 1:0.08:12). The three regioisomers have the same m/z for [M + H](+), presumably due to nucleophilic addition at the three possible electrophilic sites (C-3, -5, and -6 positions of the sulfonaniline ring). The primary adduct, R, was derived from the attack of the nucleophile at the C-5 position of the sulfonaniline ring and was determined by MS/MS and (1)H and (13)C NMR analyses. The structural assignments were confirmed by chemical synthesis of the adduct R. M2 demonstrated its electrophilic reactivity by selectively alkylating human serum albumin (HSA) at the only free thiol, Cys-34. This suggests the possibility that other proteins may undergo a similar conjugation to form irreversible adducts. Under oxidizing conditions in the presence of cumene hydroperoxide (CHP), the formation of M2 was enhanced, indicating that oxidative stress may accelerate the production of reactive diiminoquinone species (M2 and M4).

A Novel Neutrophil-specific PET Imaging Agent: CFLFLFK-PEG-64Cu

Journal of Nuclear Medicine : Official Publication, Society of Nuclear Medicine. May, 2009  |  Pubmed ID: 19372473

The synthesis and validation of a new, highly potent (64)Cu-labeled peptide, cFLFLFK-PEG-(64)Cu, that targets the formyl peptide receptor (FPR) on leukocytes is described. The peptide ligand is an antagonist of the FPR, designed not to elicit a chemotactic response resulting in neutropenia. Evidence for the selective binding of this synthesized ligand to neutrophils is provided. PET properties of the compound were evaluated in a mouse model of lung inflammation.

Blinded Evaluation of Commercial Urinary Lipoarabinomannan for Active Tuberculosis: a Pilot Study

The International Journal of Tuberculosis and Lung Disease : the Official Journal of the International Union Against Tuberculosis and Lung Disease. Aug, 2009  |  Pubmed ID: 19723379

Urine antigen testing is an attractive strategy for the diagnosis of active tuberculosis (TB), but accuracy data are scarce.

Risk Factors for MDR and XDR-TB in a Tertiary Referral Hospital in India

PloS One. 2010  |  Pubmed ID: 20209106

India has a high burden of drug resistant TB, although there are few data on XDR-TB. Although XDR-TB has existed previously in India, the definition has not been widely applied, and surveillance using second line drug susceptibility testing has not been performed. Our objective was to analyze clinical and demographic risk factors associated with isolation of MDR and XDR TB as compared to susceptible controls, at a tertiary center.

New Surface Contacts Formed Upon Reductive Lysine Methylation: Improving the Probability of Protein Crystallization

Protein Science : a Publication of the Protein Society. Jul, 2010  |  Pubmed ID: 20506323

Surface lysine methylation (SLM) is a technique for improving the rate of success of protein crystallization by chemically methylating lysine residues. The exact mechanism by which SLM enhances crystallization is still not clear. To study these mechanisms, and to analyze the conditions where SLM will provide the optimal benefits for rescuing failed crystallization experiments, we compared 40 protein structures containing N,N-dimethyl-lysine (dmLys) to a nonredundant set of 18,972 nonmethylated structures from the PDB. By measuring the relative frequency of intermolecular contacts (where contacts are defined as interactions between the residues in proximity with a distance of 3.5 A or less) of basic residues in the methylated versus nonmethylated sets, dmLys-Glu contacts are seen more frequently than Lys-Glu contacts. Based on observation of the 10 proteins with both native and methylated structures, we propose that the increased rate of contact for dmLys-Glu is due to both a slight increase in the number of amine-carboxyl H-bonds and to the formation of methyl C--H...O interactions. By comparing the relative contact frequencies of dmLys with other residues, the mechanism by which methylation of lysines improves the formation of crystal contacts appears to be similar to that of Lys to Arg mutation. Moreover, analysis of methylated structures with the surface entropy reduction (SER) prediction server suggests that in many cases SLM of predicted SER sites may contribute to improved crystallization. Thus, tools that analyze protein sequences and mark residues for SER mutation may identify proteins with good candidate sites for SLM.

Neutrophil Targeting Heterobivalent SPECT Imaging Probe: CFLFLF-PEG-TKPPR-99mTc

Bioconjugate Chemistry. Oct, 2010  |  Pubmed ID: 20843030

A new heterobivalent peptide ligand specifically targeting polymorphonuclear leukocytes (PMNs) with favorable pharmacological parameters to monitor sites of inflammation for imaging is designed. The detailed synthesis, characterization, and pharmacological evaluation of the ligands are reported here. Two separate peptide binding ligands for formyl peptide and tuftsin receptors were chosen to link together based on the high expression levels of the two receptors on activated PMNs The heterobivalency and pegylated links were incorporated in the structural design to improve the sensitivity of the detection and to improve the bioavailability along with blood clearance profile, respectively. Two chemical constructs, cFLFLF-(PEG)(n)-TKPPR-(99m)Tc (n = 4, 12), were evaluated in vitro with human PMNs for binding affinity and bioavailability. As a result, cFLFLF-(PEG)(12)-TKPPR-(99m)Tc was found to have more favorable pharmacological properties and was therefore used for further in vivo studies. Preliminary in vivo assessment of the agent was performed using single gamma emission computed tomography (SPECT) imaging of a mouse model of ear inflammation. The results of these studies indicate cFLFLF-(PEG)(12)-TKPPR-(99m)Tc may be a desirable imaging agent for binding to PMNs to identify sites of inflammation by SPECT.

Neutrophil- and Myeloperoxidase-mediated Metabolism of Reduced Nimesulide: Evidence for Bioactivation

Chemical Research in Toxicology. Nov, 2010  |  Pubmed ID: 20939553

Nimesulide, a widely used nonsteroidal anti-inflammatory drug (NSAID), has been associated with rare idiosyncratic hepatotoxicity. The chemical mechanisms underlying the liver injury remain unknown. We have undertaken the detailed study of the metabolic pathways of nimesulide in an effort to identify potential reactive metabolites. A previous report from this laboratory has demonstrated that one of the known nimesulide metabolites, termed reduced nimesulide (M1), is further bioactivated by human liver microsomes (HLMs) to form a reactive diiminoquinone species M2. The formation of M2 was confirmed indirectly by trapping with N-acetylcysteine (NAC). The aim of this study was to explore the fate of M1 in an inflammatory environment created by the recruitment of leukocytes. Leukocytes upon activation produce hydrogen peroxide (H(2)O(2)) and other myeloperoxidase (MPO) products, such as hypochlorous acid (HOCl), that are capable of metabolite oxidation. We demonstrate here that the reduced nimesulide, M1, undergoes a facile oxidation with activated neutrophils or with MPO in the presence of H(2)O(2) or HOCl to produce a variety of reactive as well as stable metabolites. One major metabolite, M3, was also produced by HLM as determined by trapping with NAC. Other metabolites, for example, M6, M8, and M9, were unique to the myeloperoxidase, because of their mode of formation from activation of the amino group of reduced nimesulide. The structures of some of these reactive metabolites were proposed on the basis of liquid chromatography-tandem mass spectrometry analyses and established by their comparison with synthetic standards. Metabolite M6 is interesting because it provides clear evidence of amine activation and indicates the potential of the reactive intermediate of M1 to conjugate with protein nucleophiles. In summary, our results demonstrate that a known nimesulide metabolite could be bioactivated by MPO through a pathway distinct from HLM-mediated pathways and that the generation of reactive species by the MPO-mediated bioactivation pathway at the site of inflammation may contribute to the toxicity associated with nimesulide.

Risk Factors for Acquiring Strongyloides Stercoralis Infection Among Patients Attending a Tertiary Hospital in South India

Indian Journal of Medical Microbiology. Apr-Jun, 2011  |  Pubmed ID: 21654109

Strongyloides stercoralis causes persistent and fatal disseminated infections in immunocompromised hosts. In this study, we aimed to determine the risk factors for acquiring strongyloidiasis and the associated morbidity in south India.

Musical Rhythm Spectra from Bach to Joplin Obey a 1/f Power Law

Proceedings of the National Academy of Sciences of the United States of America. Mar, 2012  |  Pubmed ID: 22355125

Much of our enjoyment of music comes from its balance of predictability and surprise. Musical pitch fluctuations follow a 1/f power law that precisely achieves this balance. Musical rhythms, especially those of Western classical music, are considered highly regular and predictable, and this predictability has been hypothesized to underlie rhythm's contribution to our enjoyment of music. Are musical rhythms indeed entirely predictable and how do they vary with genre and composer? To answer this question, we analyzed the rhythm spectra of 1,788 movements from 558 compositions of Western classical music. We found that an overwhelming majority of rhythms obeyed a 1/f(β) power law across 16 subgenres and 40 composers, with β ranging from ∼0.5-1. Notably, classical composers, whose compositions are known to exhibit nearly identical 1/f pitch spectra, demonstrated distinctive 1/f rhythm spectra: Beethoven's rhythms were among the most predictable, and Mozart's among the least. Our finding of the ubiquity of 1/f rhythm spectra in compositions spanning nearly four centuries demonstrates that, as with musical pitch, musical rhythms also exhibit a balance of predictability and surprise that could contribute in a fundamental way to our aesthetic experience of music. Although music compositions are intended to be performed, the fact that the notated rhythms follow a 1/f spectrum indicates that such structure is no mere artifact of performance or perception, but rather, exists within the written composition before the music is performed. Furthermore, composers systematically manipulate (consciously or otherwise) the predictability in 1/f rhythms to give their compositions unique identities.

A Novel Near-infrared Fluorescence Imaging Probe for in Vivo Neutrophil Tracking

Molecular Imaging. Sep-Oct, 2012  |  Pubmed ID: 22436637

The development and validation of a multiscopic near-infrared fluorescence (NIRF) probe, cinnamoyl-F-(D)L-F-(D)L-F-PEG-cyanine7 (cFlFlF-PEG-Cy7), that targets formyl peptide receptor on neutrophils using a mice ear inflammation model is described. Acute inflammation was induced in mice by topical application of phorbol-12-myristate-13-acetate to left ears 24 hours before probe administration. Noninvasive NIRF imaging was longitudinally performed up to 24 hours following probe injection. The in vivo neutrophil-targeting specificity of the probe was characterized by a blocking study with preadministration of excess nonfluorescent peptide cFlFlF-PEG and by an imaging study with a scrambled peptide probe cLFFFL-PEG-Cy7. NIRF imaging of mice injected with cinnamoyl-L-F-F-F-L-PEG-cyanine7 (cFlFlF-PEG-Cy7) revealed that the fluorescence intensity for inflamed left ears was approximately fourfold higher than that of control right ears at 24 hours postinjection. In comparison, the ratios acquired with the scrambled probe and from the blocking study were 1.5- and 2-fold at 24 hours postinjection, respectively. Moreover, a microscopic immunohistologic study confirmed that the NIRF signal of cFlFlF-PEG-Cy7 was associated with activated neutrophils in the inflammatory tissue. With this probe, in vivo neutrophil chemotaxis could be correlatively imaged macroscopically in live animals and microscopically at tissue and cellular levels.

Synthesis of PECAM-1-specific 64Cu PET Imaging Agent: Evaluation of Myocardial Infarction Caused by Ischemia-reperfusion Injury in Mouse

Bioorganic & Medicinal Chemistry Letters. Jun, 2012  |  Pubmed ID: 22578454

A PECAM-1 specific PET imaging agent, PECAM-1-Ab-DOTA-(64)Cu, was synthesized by conjugating the anti-mouse PECAM-1 antibody with 2,2',2",2"'-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (DOTA) and subsequent labeling with (64)Cu. Positron Emission Tomography (PET) was successfully performed in a mouse model of myocardial infarction (MI) induced by an ischemia/reperfusion (I/R) injury, indicating the elevated expression of PECAM-1.

Kidney Transplant Ureteroneocystostomy: Comparison of Full-thickness Vs. Lich-Gregoir Techniques

Clinical Transplantation. Jul-Aug, 2012  |  Pubmed ID: 22672515

Despite a variety of urinary tract reconstructive techniques, urinary complications are the most frequent technical adverse event following kidney transplantation. We examined outcomes of two ureteroneocystostomy techniques, the full-thickness (FT) technique and the Lich-Gregoir (LG) technique in 634 consecutive kidney-alone transplants (327 FT and 307 LG) between December 2006 and December 2010. Urological complications at one yr post-transplantation occurred in 27 cases (4.3%) including 16 ureteral strictures (2.5%), four ureteral obstructions (0.6%) owing to donor-derived stones or intrinsic hematoma, and seven urine leaks (1.1%). Compared with LG, the FT technique was associated with similar proportions of ureteral complications overall (3.9% vs. 4.6%, p = 0.70), ureteral strictures (3.7% vs. 1.3%, p = 0.08), urinary stones/hematoma (1.0% vs. 0.3%, p = 0.36), and overall urinary leaks (1.6% vs. 0.6%, p = 0.22); however, the FT technique was associated with somewhat fewer urine leaks at the ureterovesical junction (0% vs. 1.3%, p = 0.05). There were no differences between the two groups in terms of length of stay, delayed graft function, urinary tract infection with the first post-transplant year, estimated glomerular filtration rate, and overall graft and patient survival. The FT technique of ureteroneocystostomy is technically simple to perform and has a similar incidence of urinary complications compared with the LG technique.

A Novel Near-infrared Fluorescence Imaging Probe for in Vivo Neutrophil Tracking

Molecular Imaging. Sep-Oct, 2012  |  Pubmed ID: 22954181

The development and validation of a multiscopic near-infrared fluorescence (NIRF) probe, cinnamoyl-F-(D)L-F-(D)L-F-PEG-cyanine7 (cFlFlF-PEG-Cy7), that targets formyl peptide receptor on neutrophils using a mice ear inflammation model is described. Acute inflammation was induced in mice by topical application of phorbol-12-myristate-13-acetate to left ears 24 hours before probe administration. Noninvasive NIRF imaging was longitudinally performed up to 24 hours following probe injection. The in vivo neutrophil-targeting specificity of the probe was characterized by a blocking study with preadministration of excess nonfluorescent peptide cFlFlF-PEG and by an imaging study with a scrambled peptide probe cLFFFL-PEG-Cy7. NIRF imaging of mice injected with cinnamoyl-L-F-F-F-L-PEG-cyanine7 (cFlFlF-PEG-Cy7) revealed that the fluorescence intensity for inflamed left ears was approximately fourfold higher than that of control right ears at 24 hours postinjection. In comparison, the ratios acquired with the scrambled probe and from the blocking study were 1.5- and 2-fold at 24 hours postinjection, respectively. Moreover, a microscopic immunohistologic study confirmed that the NIRF signal of cFlFlF-PEG-Cy7 was associated with activated neutrophils in the inflammatory tissue. With this probe, in vivo neutrophil chemotaxis could be correlatively imaged macroscopically in live animals and microscopically at tissue and cellular levels.

Retropharyngeal Cold Abscess Without Pott's Spine

South African Journal of Surgery. Suid-Afrikaanse Tydskrif Vir Chirurgie. Nov, 2012  |  Pubmed ID: 23217558

Retropharyngeal abscesses are infections deep in the neck space that can pose an immediate life-threatening emergency, with potential for airway compromise and other catastrophic complications. In adults these abscesses can develop as a result of vertebral pyogenic osteomyelitis, tuberculosis of the spine, or external injuries caused by endoscopes or foreign bodies (e.g. fish bones). Tuberculosis of the retropharyngeal space is one of the rare forms of extrapulmonary tuberculosis. Early diagnosis and treatment are necessary to prevent the serious complications of the disease. We present a case of tuberculous retropharyngeal abscess in an adult woman without tuberculosis of the cervical spine who was managed surgically by aspirating the retropharyngeal abscess transorally, together with antituberculosis treatment.

Heptamethine Cyanine Based (64)Cu-PET Probe PC-1001 for Cancer Imaging: Synthesis and in Vivo Evaluation

Nuclear Medicine and Biology. Jan, 2013  |  Pubmed ID: 23375364

PURPOSE: Development of a heptamethine cyanine based tumor-targeting PET imaging probe for noninvasive detection and diagnosis of breast cancer. METHODS: Tumor-specific heptamethine-cyanine DOTA conjugate complexed with Cu-64 (PC-1001) was synthesized for breast cancer imaging. In vitro cellular uptake studies were performed in the breast cancer MCF-7 and noncancerous breast epithelial MCF-10A cell lines to establish tumor specificity. In vivo time-dependent fluorescence and PET imaging of breast tumor xenografts in mice were performed. Blood clearance, biodistribution, and tumor-specific uptake and plasma binding of PC-1001 were quantified. Tumor histology (H&E staining) and fluorescence imaging were examined. RESULTS: PC-1001 displayed similar fluorescence properties (ε=82,880cm(-1)M(-1), E(x)/E(m)=750/820nm) to the parental dye. Time-dependent cellular accumulation indicated significantly higher probe uptake (>2-fold, 30min) in MCF-7 than MCF-10A cells and the uptake was observed to be mediated by organic anion transport peptides (OATPs) system. In vivo studies revealed that PC-1001 has desirable accumulation profile in tumor tissues, with tumor versus muscle uptake of about 4.3 fold at 24h and 5.8 fold at 48h post probe injections. Blood half-life of PC-1001 was observed to be 4.3±0.2h. Microscopic fluorescence imaging of harvested tumor indicated that the uptake of PC-1001 was restricted to viable rather than necrotic tumor cells. CONCLUSIONS: A highly efficient tumor-targeting PET/fluorescence imaging probe PC-1001 is synthesized and validated in vitro in MCF-7 breast cancer cells and in vivo in mice breast cancer xenograft model.

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