Direct Interspecies Electron Transfer between Geobacter metallireducens and Methanosarcina barkeri

Direct interspecies electron transfer (DIET) is potentially an effective form of syntrophy in methanogenic communities, but little is known about the diversity of methanogens capable of DIET. The ability of Methanosarcina barkeri to participate in DIET was evaluated in coculture with Geobacter metallireducens. Cocultures formed aggregates that shared electrons via DIET during the stoichiometric conversion of ethanol to methane. Cocultures could not be initiated with a pilin-deficient G. metallireducens strain, suggesting that long-range electron transfer along pili was important for DIET. Amendments of granular activated carbon permitted the pilin-deficient G. metallireducens isolates to share electrons with M. barkeri, demonstrating that this conductive material could substitute for pili in promoting DIET. When M. barkeri was grown in coculture with the H₂-producing Pelobacter carbinolicus, incapable of DIET, M. barkeri utilized H₂ as an electron donor but metabolized little of the acetate that P. carbinolicus produced. This suggested that H₂, but not electrons derived from DIET, inhibited acetate metabolism. P. carbinolicus-M. barkeri cocultures did not aggregate, demonstrating that, unlike DIET, close physical contact was not necessary for interspecies H₂ transfer. M. barkeri is the second methanogen found to accept electrons via DIET and the first methanogen known to be capable of using either H₂ or electrons derived from DIET for CO₂ reduction. Furthermore, M. barkeri is genetically tractable, making it a model organism for elucidating mechanisms by which methanogens make biological electrical connections with other cells.     

Effectiveness of Spray Congealing to Obtain Physically Stabilized Amorphous Dispersions of a Poorly Soluble Thermosensitive API

An amorphous phase produced by micronization up to the molecular or colloidal level of a poorly soluble drug having low lipophilicity can distinctly enhance its solubility characteristics. However, though dispersing the molten mass of a poorly water-soluble drug within polymeric matrix has been found to be most effective in formation of molecular dispersions, the drug molecules which melt at high temperature also accompanied by decomposition, such as acetazolamide, are difficult to formulate as molecular dispersions. Hence, a method is proposed to obtain molecular dispersions of acetazolamide with poloxamer-237 by spray congealing under optimal heat treatment. Uniform molecular and/or colloidal dispersions of the drug were achieved with instantaneous solvent evaporation by mixing a drug solution with molten mass of the plasticizer matrix. Immobilization of dispersed drug molecules was effected subsequently through rapid solidification by spray congealing. Initial characterization of 1:1, 1:1.5, and 1:2 ratios of solid dispersions and devitrification study of an optimized (1:2) ratio ensured efficacy of the proposed method in formation of physically stabilized amorphous systems without thermal degradation and hence resulted in more than ninefold rise in solubility and more than 90% dissolution within initial 10 min. With 1:2 ratio, molecular dispersions could be achieved by initial solvent evaporation stage, which when subjected to spray congealing produced physically stable amorphous systems, without signs of thermal degradation. This study also proposes an opportunity for selection of those polymers with which the drug is immiscible in their fluid state, yet obtaining molecular dispersions.KEY WORDS: low molecular lipophilicity, melt with decomposition, rapid solidification, solid solutions     

The isolation of novel mesenchymal stromal cell chemotactic factors from the conditioned medium of tumor cells

Bone marrow-derived mesenchymal stromal cells (MSCs) localize to solid tumors. Defining the signaling mechanisms that regulate this process is important in understanding the role of MSCs in tumor growth. Using a combination of chromatography and electrospray tandem mass spectrometry we have identified novel soluble signaling molecules that induce MSC chemotaxis present in conditioned medium of the breast carcinoma cell line MDA-MB231. Previous work has employed survey strategies using ELISA assay to identify known chemokines that promote MSC chemotaxis. While these studies provide valuable insights into the intercellular signals that impact MSC behavior, many less well-described, but potentially important soluble signaling molecules could be overlooked using these methods. Through the less directed method of column chromatography we have identified novel candidate MSC chemotactic peptides. Two proteins, cyclophilin B and hepatoma-derived growth factor were then further characterized and shown to promote MSC chemotaxis.     

Protein tyrosine nitration of the flavin subunit is associated with oxidative modification of mitochondrial complex II in the post-ischemic myocardium

Increased O(2)* and NO production is a key mechanism of mitochondrial dysfunction in myocardial ischemia/reperfusion injury. A crucial segment of the mitochondrial electron transport chain is succinate ubiquinone reductase (SQR or Complex II). In SQR, oxidative impairment and deglutathionylation of the 70-kDa flavin protein occurs in the post-ischemic heart ( Chen, Y. R., Chen, C. L., Pfeiffer, D. R., and Zweier, J. L. (2007) J. Biol. Chem. 282, 32640-32654 ). To gain insights into the oxidative modification of the 70-kDa protein in the post-ischemic myocardium, we used the identified S-glutathionylated peptide ((77)AAFGLSEAGFNTACVTK(93)) of the 70-kDa protein as a chimeric epitope incorporating a "promiscuous" T cell epitope to generate a high titer polyclonal antibody, AbGSC90. Purified AbGSC90 showed a high binding affinity to isolated SQR. Antibodies of AbGSC90 moderately inhibited the electron transfer and superoxide generation activities of SQR. To test for protein nitration, rats were subjected to 30 min of coronary ligation followed by 24 h of reperfusion. Tissue homogenates were immunoprecipitated with AbGSC90 and probed with antibodies against 3-nitrotyrosine. Enhancement of protein tyrosine nitration was detected in the post-ischemic myocardium. Isolated SQR was subjected to in vitro protein nitration with peroxynitrite, leading to site-specific nitration at the 70-kDa polypeptide and impairment of SQR electron transfer activity. Protein nitration of SQR further impaired its protein-protein interaction with Complex III. Liquid chromatography/tandem mass spectrometry analysis indicated that Tyr-56 and Tyr-142 were involved in protein tyrosine nitration. When the isolated SQR was subjected to in vitro S-glutathionylation, oxidative modification and impairment mediated by peroxynitrite were significantly decreased, thus confirming the protective effect of S-glutathionylation from the oxidative damage of nitration.     

Depletion of the ATPase NSF from Golgi membranes with hypo-S-nitrosylation of vasorelevant proteins in endothelial cells exposed to monocrotaline pyrrole

Investigations of regulated S-nitrosylation and denitrosylation of vasorelevant proteins are a newly emergent area in vascular biology. We previously showed that monocrotaline pyrrole (MCTP)-induced megalocytosis of pulmonary arterial endothelial cells (PAECs), which underlies the development of pulmonary arterial hypertension, was associated with a Golgi blockade characterized by the trapping of diverse vesicle tethers, soluble N-ethylmaleimide-sensitive factor (NSF)-attachment protein receptors (SNAREs), and soluble NSF-attachment proteins (SNAPs) in the Golgi; reduced trafficking of caveolin-1 (cav-1) and endotheial nitric oxide (NO) synthase (eNOS) from the Golgi to the plasma membrane; and decreased caveolar NO. We have investigated whether NSF, the ATPase involved in all SNARE disassembly, might be the upstream target of MCTP and whether MCTP might regulate NSF by S-nitrosylation. Immunofluorescence microscopy and Golgi purification techniques revealed the discordant decrease of NSF by approximately 50% in Golgi membranes after MCTP despite increases in alpha-SNAP, cav-1, eNOS, and syntaxin-6. The NO scavenger (4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide failed to affect the initiation or progression of MCTP megalocytosis despite a reduction of 4,5-diaminofluorescein diacetate fluorescence and inhibition of S-nitrosylation of eNOS as assayed using the biotin-switch method. Moreover, the latter assay not only revealed constitutive S-nitrosylation of NSF, eNOS, cav-1, and clathrin heavy chain (CHC) in PAECs but also a dramatic 70-95% decrease in the S-nitrosylation of NSF, eNOS, cav-1, and CHC after MCTP. These data point to depletion of NSF from Golgi membranes as a mechanism for Golgi blockade after MCTP and to denitrosylation of vasorelevant proteins as critical to the development of endothelial cell megalocytosis.     

Novel 3,3-disubstituted pyrrolidines as selective triple serotonin/norepinephrine/dopamine reuptake inhibitors

A series of 3,3-disubstituted pyrrolidine monoamine triple reuptake inhibitors were discovered. Analogues with low nanomolar potency, good human in vitro microsomal stability and in vitro permeability, and low drug-drug interaction potential are described. One example showed in vivo anti-depressant-like effects in the mouse tail suspension assay with a minimum effective dose of 30 mg/kg i.p.     

Mineral supported facile synthesis of novel 4-hydroxybenzoxazin-2-thione N-nucleosides

One-pot montmorillonite K-10 clay-supported reactions of substituted/unsubstituted salicylaldehyde and ribosyl/deoxyribosyl thioureas expeditiously yielded novel N-nucleosides, 4-hydroxy-3,4-dihydro-3-(beta-D-ribofuranosyl or beta-D-2'-deoxyribofuranosyl)-2'-benz[e]-1,3-oxazin-2-thione via cycloisomerization of aldehyde intermediate under solvent-free microwave irradiation conditions.     

Ligation and mucopexy for prolapsing hemorrhoids – a ten year experience

Objective

The aim of this study is to clinically test the efficacy of author's approach of suture ligation and mucopexy for patients having symptomatic and prolapsing hemorrhoids.

Materials and methods

616 patients (255 females) complaining of symptoms of hemorrhoids were included in the study. The hemorrhoids were suture ligated with an absorbable suture material under vision. Operating time, postoperative complications, time to return to work, and outcome of the procedure were analyzed. Follow-up was planned following discharge after 1 month, 6 months and after at least 1 year. Patient satisfaction was also assessed.

Results

The mean procedure time was 8 ± 0 minutes (range, 6–15 minutes), and the total admission period was 12 ± 4 Hours. Perianal thrombosis and skin tags were the commonest post-operative complications. The mean total analgesic dose and duration of pain control using analgesics was 19 ± 4 tablets, and 9 ± 3 days respectively. The postoperative follow up after 4 weeks revealed therapeutic success in 589 patients (95.6%), who presented with hemorrhoidal bleeding. Prolapse was no longer observed in 98% of patients and 96% patients experienced no pain after defecation. 93% patients completed the one-year follow-up and 89 percent of them were asymptomatic. The patient satisfaction scoring was 8.2% on visual analogue scale.

Conclusion

Suture ligation and mucopexy of hemorrhoids is an easy-to-perform technique that is well accepted by patients and has good results for prolapsing hemorrhoids.     

NLScore: a novel quantitative algorithm based on 3 dimensional structural determinants to predict the probability of nuclear localization in proteins containing classical nuclear localization signals

The presence of a nuclear localization signal (NLS) in proteins can be inferred by the presence of a stretch of basic amino acids (KRKK). These NLSs are termed classical NLS (cNLS). However, only a fraction of proteins containing the cNLS pattern are transported into the nucleus by binding to importin α. Hence, there must exist, additional structural determinants that guide the appropriate interaction between putative NLSs containing cargo and importin α. Using 52 protein structures containing cNLS obtained from RCSB PDB, we assembled a training set and a validation set such that both sets were comprised of a combination of proteins with proven nuclear localization and ones that were non-nuclear. We modeled the interface between cargoes containing cNLS and importin α. We conducted rigid body docking and produced induced-fit modes by allowing both side chain and the backbone to be flexible. The output of these studies and additional determinants such as energy of interaction, atomic contacts, hydrophilic interaction, cationic interaction, and penetration of the cargo protein were used to derive a 26 parameter quantitative structure activity relationship based regression equation. This was further optimized by a step-wise backward elimination approach to derive a 15 parameter score. This NLScore was not only able to correctly classify confirmed nuclear and non-nuclear localized proteins but it was able to perform better than currently implemented algorithms like NucPred, Euk-mPLoc 2.0, cNls Mapper, and NLStradamus. Leave-one-out cross validation (LOOCV) showed that NLScore correctly predicted 78.6% and 81.6% of non-nuclear and nuclear proteins respectively.

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Graphical abstract NLScore: a novel quantitative algorithm based on 3 dimensional structural determinants to predict the probability of nuclear localization in proteins

     

Synthetic α-(aminomethyl)-γ-butyrolactones and their anti-pancreatic cancer activities

Aminated α-methylene-γ-butyrolactones, which are readily synthesized with facile control of the diastereoisomerism, provide an economical and commercially-viable alternative to the use of aminated natural products. These aminoloactones, which exhibit excellent activity against three pancreatic cancer cell lines when measured at 10 μM—Panc-1, MIA PaCa-2, and BxPC-3—and are comparable to or better than parthenolide and dimethylaminoparthenolide (DMAPT, LC-1). It has also been shown that there is an effect on the biological activity depending on the identity of the amine.