bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative imaging of murine osteoarthritic cartilage by phase‐contrast micro–computed tomography
Authors: Ruan Merry Z. C. , Dawson Brian , Jiang Ming‐Ming , Gannon Francis , Heggeness Michael , Lee Brendan H. L.
Published: November 2012

Objective

The mouse is an optimal model organism in which gene–environment interactions can be used to study the pathogenesis of osteoarthritis (OA). The gold standard for arthritis research in mice is based on histopathology and immunohistochemistry, which are labor‐intensive, prone to sampling bias and technical variability, and limited in throughput. The aim of this study was to develop a new technique that assesses mouse cartilage by integrating quantitative volumetric imaging techniques.

Methods

A novel mouse model of OA was generated by cruciate ligament transection (CLT) and evaluated by histopathology and immunohistochemistry. Knee joint specimens were then imaged using a new technique that combines high‐resolution micro–computed tomography (micro‐CT) and phase‐contrast optics followed by quantitative analyses. A comparative analysis was also performed in a previously established mouse model of OA generated by destabilization of the medial meniscus (DMM).

Results

Phase‐contrast micro‐CT achieved cellular resolution of chondrocytes and quantitative assessment of parameters such as articular cartilage volume and surface area. In mouse models of OA generated by either CLT or DMM, we showed that phase‐contrast micro‐CT distinguished control and OA cartilage by providing quantitative measures with high reproducibility and minimal variability. Features of OA at the cellular or tissue level could also be observed in images generated by phase‐contrast micro‐CT.

Conclusion

We established an imaging technology that comprehensively assessed and quantified the 2‐dimensional and 3‐dimensional changes of articular cartilage. Application of this technology will facilitate the rapid and high‐throughput assessment of genetic and therapeutic models of OA in mice.
Stimulation of superficial zone protein accumulation by hedgehog and Wnt signaling in surface zone bovine articular chondrocytes
Authors: Iwakura Takashi , Inui Atsuyuki , Reddi A. Hari
Published: November 2012

Objective

To determine the roles of the hedgehog and Wnt signaling pathways in accumulation of superficial zone protein (SZP) in surface zone articular chondrocytes.

Methods

Explant cultures of disks of surface zone cartilage or isolated chondrocytes from the surface zone of articular cartilage of bovine stifle joints were cultured in serum‐free chemically defined medium. Accumulation of SZP in the culture medium, in response to hedgehog proteins (sonic hedgehog [SHH] and Indian hedgehog [IHH]), Wnt proteins (Wnt‐3a, Wnt‐5a, and Wnt‐11), agonists of the Wnt/β‐catenin pathway (glycogen synthase kinase 3β [GSK‐3β] inhibitors), and antagonists of the Wnt/β‐catenin pathway, was investigated. The interaction between transforming growth factor β1 (TGFβ1) and hedgehog proteins or antagonists of the Wnt/β‐catenin pathway was also investigated.

Results

Hedgehog proteins stimulated SZP accumulation. Activation of the Wnt/β‐catenin pathway by Wnt‐3a and GSK‐3β inhibitors led to inhibition of SZP accumulation; however, Wnt‐5a and Wnt‐11 had no influence on SZP accumulation. Conversely, antagonists of the Wnt/β‐catenin pathway stimulated SZP accumulation. In addition, there were combinatorial effects of TGFβ1 and hedgehog proteins or antagonists of the Wnt/β‐catenin pathway on SZP accumulation.

Conclusion

SHH and IHH signaling has a stimulatory effect on SZP accumulation in surface zone cartilage and isolated articular chondrocytes. These findings provide insight into the regulatory mechanisms of articular cartilage homeostasis and maintenance by morphogens.
Clinical significance of organic anion transporting polypeptides (OATPs) in drug disposition: their roles in hepatic clearance and intestinal absorption
Authors: Shitara Yoshihisa , Maeda Kazuya , Ikejiri Kazuaki , Yoshida Kenta , Horie Toshiharu , Sugiyama Yuichi
Published: November 2012

Organic anion transporting polypeptide (OATP) family transporters accept a number of drugs and are increasingly being recognized as important factors in governing drug and metabolite pharmacokinetics. OATP1B1 and OATP1B3 play an important role in hepatic drug uptake while OATP2B1 and OATP1A2 might be key players in intestinal absorption and transport across blood–brain barrier of drugs, respectively. To understand the importance of OATPs in the hepatic clearance of drugs, the rate‐determining process for elimination should be considered; for some drugs, hepatic uptake clearance rather than metabolic intrinsic clearance is the more important determinant of hepatic clearances. The importance of the unbound concentration ratio (liver/blood), Kp,uu, of drugs, which is partly governed by OATPs, is exemplified in interpreting the difference in the IC50 of statins between the hepatocyte and microsome systems for the inhibition of HMG‐CoA reductase activity. The intrinsic activity and/or expression level of OATPs are affected by genetic polymorphisms and drug–drug interactions. Their effects on the elimination rate or intestinal absorption rate of drugs may sometimes depend on the substrate drug. This is partly because of the different contribution of OATP isoforms to clearance or intestinal absorption. When the contribution of the OATP‐mediated pathway is substantial, the pharmacokinetics of substrate drugs should be greatly affected. This review describes the estimation of the contribution of OATP1B1 to the total hepatic uptake of drugs from the data of fold‐increases in the plasma concentration of substrate drugs by the genetic polymorphism of this transporter. To understand the importance of the OATP family transporters, modeling and simulation with a physiologically based pharmacokinetic model are helpful. Copyright © 2012 John Wiley & Sons, Ltd.
Modulation of the shape and speed of a chemical wave in an unstirred Belousov–Zhabotinsky reaction by a rotating magnet
Authors: Okano Hideyuki , Kitahata Hiroyuki
Published: November 2012

The objective of this study was to observe whether a rotating magnetic field (RMF) could change the anomalous chemical wave propagation induced by a moderate‐intensity gradient static magnetic field (SMF) in an unstirred Belousov–Zhabotinsky (BZ) reaction. The application of the SMF (maximum magnetic flux density = 0.22 T, maximum magnetic flux density gradient = 25.5 T/m, and peak magnetic force product (flux density × gradient) = 4 T2/m) accelerated the propagation velocity in a two‐dimensional pattern. Characteristic anomalous patterns of the wavefront shape were generated and the patterns were dependent on the SMF distribution. The deformation and increase in the propagation velocity were diminished by the application of an RMF at a rotation rate of 1 rpm for a few minutes. Numerical simulation by means of the time‐averaged value of the magnetic flux density gradient or the MF gradient force over one rotation partially supported the experimental observations. These considerations suggest that RMF exposure modulates the chemical wave propagation and that the degree of modulation could be, at least in part, dependent on the time‐averaged MF distribution over one rotation. Bioelectromagnetics 34:220–230, 2013. © 2012 Wiley Periodicals, Inc.
Adventures in peptides and science with students! the joys of research
Authors: Hruby Victor J.
Published: November 2012

Working with students at the undergraduate, graduate and postdoctoral levels has brought me great joy and satisfaction. Each student is a unique human being, so each provides an important opportunity for learning, creativity and accomplishment in research and scholarship. In this reflection, several examples of this scientific process are discussed in the context of solving scientific problems which led to novel and critical scientific insights. © 2012 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 127–131, 2013.
Co‐hydrolysis of lignocellulosic biomass for microbial lipid accumulation
Authors: Ruan Zhenhua , Zanotti Michael , Zhong Yuan , Liao Wei , Ducey Chad , Liu Yan
Published: November 2012

The herbaceous perennial energy crops miscanthus, giant reed, and switchgrass, along with the annual crop residue corn stover, were evaluated for their bioconversion potential. A co‐hydrolysis process, which applied dilute acid pretreatment, directly followed by enzymatic saccharification without detoxification and liquid–solid separation between these two steps was implemented to convert lignocellulose into monomeric sugars (glucose and xylose). A factorial experiment in a randomized block design was employed to optimize the co‐hydrolysis process. Under the optimal reaction conditions, corn stover exhibited the greatest total sugar yield (glucose + xylose) at 0.545 g g−1 dry biomass at 83.3% of the theoretical yield, followed by switch grass (0.44 g g−1 dry biomass, 65.8% of theoretical yield), giant reed (0.355 g g−1 dry biomass, 64.7% of theoretical yield), and miscanthus (0.349 g g−1 dry biomass, 58.1% of theoretical yield). The influence of combined severity factor on the susceptibility of pretreated substrates to enzymatic hydrolysis was clearly discernible, showing that co‐hydrolysis is a technically feasible approach to release sugars from lignocellulosic biomass. The oleaginous fungus Mortierella isabellina was selected and applied to the co‐hydrolysate mediums to accumulate fungal lipids due to its capability of utilizing both C5 and C6 sugars. Fungal cultivations grown on the co‐hydrolysates exhibited comparable cell mass and lipid production to the synthetic medium with pure glucose and xylose. These results elucidated that combining fungal fermentation and co‐hydrolysis to accumulate lipids could have the potential to enhance the utilization efficiency of lignocellulosic biomass for advanced biofuels production. Biotechnol. Bioeng. 2013; 110: 1039–1049. © 2012 Wiley Periodicals, Inc.
Balancing redox cofactor generation and ATP synthesis: Key microaerobic responses in thermophilic fermentations
Authors: Loftie‐Eaton Wesley , Taylor Mark , Horne Kerry , Tuffin Marla I. , Burton Stephanie G. , Cowan Don A.
Published: November 2012

Geobacillus thermoglucosidasius is a Gram‐positive, thermophilic bacterium capable of ethanologenic fermentation of both C5 and C6 sugars and may have possible use for commercial bioethanol production [Tang et al., 2009; Taylor et al. (2009) Trends Biotechnol 27(7): 398–405]. Little is known about the physiological changes that accompany a switch from aerobic (high redox) to microaerobic/fermentative (low redox) conditions in thermophilic organisms. The changes in the central metabolic pathways in response to a switch in redox potential were analyzed using quantitative real‐time PCR and proteomics. During low redox (fermentative) states, results indicated that glycolysis was uniformly up‐regulated, the Krebs (tricarboxylic acid or TCA) cycle non‐uniformly down‐regulated and that there was little to no change in the pentose phosphate pathway. Acetate accumulation was accounted for by strong down‐regulation of the acetate CoA ligase gene (acs) in addition to up‐regulation of the pta and ackA genes (involved in acetate production), thus conserving ATP while reducing flux through the TCA cycle. Substitution of an NADH dehydrogenase (down‐regulated) by an up‐regulated NADH:FAD oxidoreductase and up‐regulation of an ATP synthase subunit, alongside the observed shifts in the TCA cycle, suggested that an oxygen‐scavenging electron transport chain likely remained active during low redox conditions. Together with the observed up‐regulation of a glyoxalase and down‐regulation of superoxide dismutase, thought to provide protection against the accumulation of toxic phosphorylated glycolytic intermediates and reactive oxygen species, respectively, the changes observed in G. thermoglucosidasius NCIMB 11955 under conditions of aerobic‐to‐microaerobic switching were consistent with responses to low pO2 stress. Biotechnol. Bioeng. 2013; 110: 1057–1065. © 2012 Wiley Periodicals, Inc.
Optimized signal peptides for the development of high expressing CHO cell lines
Authors: Kober Lars , Zehe Christoph , Bode Juergen
Published: November 2012

Recombinant biotherapeutic proteins such as monoclonal antibodies are mostly produced in Chinese hamster ovary (CHO) cells and pharmaceutical companies are interested in an appropriate platform technology for the development of large‐scale production processes. A major aim of our study was therefore to improve the secretion efficiency of a recombinant biotherapeutic antibody by optimizing signal peptides. Reporter molecules such as gaussia and vargula luciferase or secreted alkaline phosphatase are frequently used to this end. In striking contrast, we used a biotherapeutic antibody that was fused to 16 different signal peptides during our study. In this way, the secretion efficiency of the recombinant antibody has been analyzed by transient expression experiments in CHO cell lines. Compared to the control signal peptide, it was not possible to achieve higher efficiencies with signal peptides derived from a variety of species or even natural immunoglobulin G signal peptides. The best results were obtained with natural signal peptides derived from human albumin and human azurocidin. These results were confirmed by fed‐batch experiments with stably transfected cell pools, in which cell‐specific productivities up to 90 pg cell−1 day−1 and product concentrations up to 4 g L−1 could be determined using the albumin signal peptide. Finally, the applicability of the identified signal peptides for both different antibodies and non‐antibody products was demonstrated by transient expression experiments. In conclusion, it was found that signal peptides derived from human albumin and human azurocidin are most appropriate to generate cell lines with clearly improved production rates suitable for commercial purposes in a product‐independent manner. Biotechnol. Bioeng. 2013; 110: 1164–1173. © 2012 Wiley Periodicals, Inc.
In silico multi‐scale model of transport and dynamic seeding in a bone tissue engineering perfusion bioreactor
Authors: Spencer T.J. , Hidalgo‐Bastida L.A. , Cartmell S.H. , Halliday I. , Care C.M.
Published: November 2012

Computer simulations can potentially be used to design, predict, and inform properties for tissue engineering perfusion bioreactors. In this work, we investigate the flow properties that result from a particular poly‐L‐lactide porous scaffold and a particular choice of perfusion bioreactor vessel design used in bone tissue engineering. We also propose a model to investigate the dynamic seeding properties such as the homogeneity (or lack of) of the cellular distribution within the scaffold of the perfusion bioreactor: a pre‐requisite for the subsequent successful uniform growth of a viable bone tissue engineered construct. Flows inside geometrically complex scaffolds have been investigated previously and results shown at these pore scales. Here, it is our aim to show accurately that through the use of modern high performance computers that the bioreactor device scale that encloses a scaffold can affect the flows and stresses within the pores throughout the scaffold which has implications for bioreactor design, control, and use. Central to this work is that the boundary conditions are derived from micro computed tomography scans of both a device chamber and scaffold in order to avoid generalizations and uncertainties. Dynamic seeding methods have also been shown to provide certain advantages over static seeding methods. We propose here a novel coupled model for dynamic seeding accounting for flow, species mass transport and cell advection‐diffusion‐attachment tuned for bone tissue engineering. The model highlights the timescale differences between different species suggesting that traditional homogeneous porous flow models of transport must be applied with caution to perfusion bioreactors. Our in silico data illustrate the extent to which these experiments have the potential to contribute to future design and development of large‐scale bioreactors. Biotechnol. Bioeng. 2013; 110: 1221–1230. © 2012 Wiley Periodicals, Inc.
Polymer characterization and optimization of conditions for the enhanced bioproduction of benzaldehyde by Pichia pastoris in a two‐ ;phase partitioning bioreactor
Authors: Craig Tom , Daugulis Andrew J.
Published: November 2012

Benzaldehyde, with its apricot and almond‐like aroma, is the second most abundantly used molecule in the flavor industry, and is most commonly produced via chemical routes, such as by the oxidation of toluene. Biologically produced benzaldehyde, whether by extraction of plant material or via microbial biotransformation, commands a substantial price advantage, and greater consumer acceptance. Methylotrophic yeast, such as Pichia pastoris, contain the enzyme alcohol oxidase (AOX), which, in the presence of alcohols other than methanol, are able to yield aldehydes as dead‐end products, for example, benzaldehyde from benzyl alcohol. In this work, we have determined that benzaldehyde, and not benzyl alcohol, is inhibitory to the transformation reaction by P. pastoris, prompting the development of a selection strategy for identifying sequestering polymers for use in a partitioning bioreactor that was based on the ratio of partition coefficients (PCs) for the two target molecules. Additionally, we have now confirmed for the first time, that the mechanism of solute uptake by amorphous polymers is via absorption, not adsorption. Finally, we have adopted a common strategy used for the production of heterologous proteins by P. pastoris, namely the use of a mixed methanol/glycerol feed for inducing the required AOX enzyme, while reducing the time required for high density biomass generation. All of these components were combined in a final experiment in which 10% of the polymer Kraton D1102K, whose PC ratio of benzaldehyde to benzyl alcohol was 14.9, was used to detoxify the biotransformation in a 5 L partitioning bioreactor, resulting in a 3.4‐fold increase in benzaldehyde produced (14.4 g vs. 4.2 g) relative to single phase operation, at more than double the volumetric productivity (97 mg L−1 h−1 vs. 41 mg L−1 h−1). Biotechnol. Bioeng. 2013; 110: 1098–1105. © 2012 Wiley Periodicals, Inc.
Model‐based analysis on the extractability of information from data in dynamic fed‐batch experiments
Authors: Wechselberger Patrick , Sagmeister Patrick , Herwig Christoph
Published: November 2012

Dynamic changes of physiological bioprocess parameters, e.g. a change in the specific growth rate μ, are frequently observed during industrial manufacturing as well as bioprocess development. A quantitative description of these variations is of great interest, since it can bring elucidation to the physiological state of the culture. The goal of this contribution was to show limitations and issues for the calculation of rates with regard to temporal resolution for dynamic fed‐batch experiments. The impact of measurement errors, temporal resolution and the physiological activity on the signal to noise ratio (SNR) of the calculated rates was evaluated using an in‐silico approach. To make use of that in practice, a generally applicable rule of thumb equation for the estimation of the SNR of specific rates was presented. The SNR calculated by this rule of thumb equation helps with definition of sampling intervals and making a decision whether an observed change is statistically significant or should be attributed to random error. Furthermore, a generic reconciliation approach to remove random as well as systematic error from data was presented. This reconciliation technique requires only little prior knowledge. The validity of the proposed tools was checked with real data from a fed‐batch culture of E. coli with dynamic variations due to feed profile. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 2013
Recombinant expression and purification of the antimicrobial peptide magainin‐2
Authors: Ramos Reinaldo , Moreira Susana , Rodrigues Ana , Gama Miguel , Domingues Lucília
Published: November 2012

Magainin‐2 (MAG2) is a polycationic antimicrobial peptide isolated from the skin of the African clawed frog Xenopus laevis. It has a wide spectrum of antimicrobial activities against gram‐positive and gram‐negative bacteria, fungi, and induces osmotic lysis of protozoa. MAG2 also possesses antiviral and antitumoral properties. These activities make this peptide a promising candidate for therapeutic applications. Recombinant expression systems are necessary for the affordable production of large amounts of the biologically active peptide. In this work, MAG2 has been cloned to the N‐terminal of a family III carbohydrate‐binding module fused to the linker sequence (LK‐CBM3) from Clostridium thermocellum; a formic acid recognition site was introduced between the two modules for chemical cleavage of the peptide. The recombinant protein MAG2‐LK‐CBM3 was expressed in Escherichia coli BL21 (DE3) and MAG2 was successfully cleaved and purified from the fusion partner LK‐CBM3. Its functionality was confirmed by testing its activity against gram‐negative bacteria. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013
Immobilization of Oenococcus oeni in lentikats® to develop malolactic fermentation in wines
Authors: Rodríguez‐Nogales José Manuel , Vila‐Crespo Josefina , Fernández‐Fernández Encarnación
Published: November 2012

Entrapment of Oenococcus oeni into a polymeric matrix based on polyvinyl alcohol (PVA) (Lentikats®) was successfully used to get a better development of malolactic fermentation (MLF) in wine. The incubation of immobilized cells in a nutrient medium before starting the MLF, did not improve the degradation of malic acid. In only one day, 100% of conversion of malic acid was achieved using a high concentration of immobilized cells (0.35 g gel/ml of wine with a cell‐loading of 0.25 mg cells/mg of gel). While a low concentration of 0.21 g gel/ml of wine (cell‐loading of 0.25 mg cells/mg of gel) needed 3 days to get a reduction of 40%. The entrapped cells could be reused through six cycles (runs of 3 days), retaining 75% of efficacy for the conversion of malic acid into lactic acid. The immobilized cells in PVA hydrogels gave better performance than free cells because of the increase of the alcohol toleration. Consequently, the inhibitory effect of ethanol for developing MLF could be reduced using immobilized cells into PVA hydrogels. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013
Avidity‐mediated virus separation using a hyperthermophilic affinity ligand
Authors: Hussain Mahmud , Lockney Dustin , Wang Ruqi , Gera Nimish , Rao Balaji M.
Published: November 2012

Immunoaffinity separation of large multivalent species such as viruses is limited by the stringent elution conditions necessary to overcome their strong and highly avid interaction with immobilized affinity ligands on the capture surface. Here we present an alternate strategy that harnesses the avidity effect to overcome this limitation. Red clover necrotic mosaic virus (RCNMV), a plant virus relevant to drug delivery applications, was chosen as a model target for this study. An RCNMV binding protein (RBP) with modest binding affinity (KD ∼100 nM) was generated through mutagenesis of the Sso7d protein from Sulfolobus solfataricus and used as the affinity ligand. In our separation scheme, RCNMV is captured by a highly avid interaction with RBP immobilized on a nickel surface through a hexahistidine (6xHis) tag. Subsequently, disruption of the multivalent interaction and release of RCNMV is achieved by elution of RBP from the nickel surface. Finally, RCNMV is separated from RBP by exploiting the large difference in their molecular weights (∼8 MDa vs. ∼10 kDa). Our strategy not only eliminates the need for harsh elution conditions, but also bypasses chemical conjugation of the affinity ligand to the capture surface. Stable non‐antibody affinity ligands to a wide spectrum of targets can be generated through mutagenesis of Sso7d and other hyperthermophilic proteins. Therefore, our approach may be broadly relevant to cases where capture of large multivalent species from complex mixtures and subsequent release without the use of harsh elution conditions is necessary. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013
Fed‐batch CHO cell t‐PA production and feed glutamine replacement to reduce ammonia production
Authors: Kim Do Yun , Chaudhry Muhammad Arshad , Kennard Malcolm L. , Jardon Mario A. , Braasch Katrin , Dionne Ben , Butler Michael , Piret James M.
Published: November 2012

Industrial therapeutic protein production has been greatly improved through fed‐batch development. In this study, improvement to the productivity of a tissue‐plasminogen activator (t‐PA) expressing Chinese hamster ovary (CHO) cell line was investigated in shake flask culture through the optimization of the fed‐batch feed and the reduction of ammonia generation by glutamine replacement. The t‐PA titer was increased from 33 mg/L under batch conditions to 250 mg/L with daily feeding starting after three days of culture. A commercially available fed‐batch feed was supplemented with cotton seed hydrolysate and the four depleted amino acids, aspartic acid, asparagine, cysteine, and tyrosine. The fed‐batch operation increased the generation of by‐products such as lactate and ammonia that can adversely affect the fed‐batch performance. To reduce the ammonia production, a glutamine‐containing dipeptide, pyruvate, glutamate, and wheat gluten hydrolysate, were investigated as glutamine substitutes. To minimize the lag phase as the cells adjusted to the new energy source, a feed glutamine replacement process was developed where the cells were initially cultured with a glutamine containing basal medium to establish cell growth followed by feeding with a feed containing the glutamine substitutes. This two‐step feed glutamine replacement process not only reduced the ammonia levels by over 45% but, in the case of using wheat gluten hydrolysate, almost doubled the t‐PA titer to over 420 mg/L without compromising the t‐PA product quality or glycosylation pattern. The feed glutamine replacement process combined with optimizing other feed medium components provided a simple, practical, and effective fed‐batch strategy that could be applied to the production of other recombinant therapeutic proteins. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013
Solubility properties and diffusional extraction behavior of natamycin from streptomyces gilvosporeus biomass
Authors: Zeng Xianhai , Danquah Michael K. , Jing Keju , Woo Meng Wai , Chen Xiao Dong , Xie Youping , Lu Yinghua
Published: November 2012

Natamycin is a type of polyene macrolide antibiotic and has been produced in submerged microbial cultures of some natural Streptomyces strains. Natamycin extraction from cellular biomass is greatly affected by the molecular and solubilization characteristics of the extraction solvent, and this is a major reason for the routine attainment of low volumetric titers, resulting from sparing natamycin solubility. In this work, a series of experiments were conducted to investigate the solubility of natamycin in some selected organic solvents in order to assess the influence on natamycin extraction yield. Natamycin showed the highest solubility in 75% aqueous methanol under the conditions of pH 2, 30°C and 1 atm. Furthermore, the extraction of natamycin using 75% aqueous methanol was performed and the highest extraction yield of 45.7% was obtained under pH 2. A mathematical model derived from Fick's law of the biomolecular diffusion process was developed to fit the experimental kinetic data of natamycin extraction. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013
Optimization of a two‐step process comprising lipase catalysis and thermal cyclization improves the efficiency of synthesis of six‐membered cyclic carbonate from trimethylolpropane and dimethylcarbonate
Authors: Bornadel Amin , Hatti‐Kaul Rajni , Sörensen Kent , Lundmark Stefan , Pyo Sang‐Hyun
Published: November 2012

Six‐membered cyclic carbonates are potential monomers for phosgene and/or isocyanate free polycarbonates and polyurethanes via ring‐opening polymerization. A two‐step process for their synthesis comprising lipase‐catalyzed transesterification of a polyol, trimethylolpropane (TMP) with dimethylcarbonate (DMC) in a solvent‐free system followed by thermal cyclization was optimized to improve process efficiency and selectivity. Using full factorial designed experiments and partial least squares (PLS) modeling for the reaction catalyzed by Novozym®435 (N435; immobilized Candida antarctica lipase B), the optimum conditions for obtaining either high proportion of monocarbonated TMP and TMP‐cyclic‐carbonate (3 and 4), or dicarbonated TMP and monocarbonated TMP‐cyclic‐carbonate (5 and 6) were found. The PLS model predicted that the reactions using 15%–20% (w/w) N435 at DMC:TMP molar ratio of 10–30 can reach about 65% total yield of 3 and 4 within 10 h, and 65%–70% total yield of 5 and 6 within 32–37 h, respectively. High consistency between the predicted results and empirical data was shown with 66.1% yield of 3 and 4 at 7 h and 67.4% yield of 5 and 6 at 35 h, using 18% (w/w) biocatalyst and DMC:TMP molar ratio of 20. Thermal cyclization of the product from 7 h reaction, at 110°C in the presence of acetonitrile increased the overall yield of cyclic carbonate 4 from about 2% to more than 75% within 24 h. N435 was reused for five consecutive batches, 10 h each, to give 3+4 with a yield of about 65% in each run. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013.
Osteogenic differentiation and osteochondral tissue engineering using human adipose‐derived stem cells
Authors: Mahmoudifar Nastaran , Doran Pauline M.
Published: November 2012

Osteogenesis and the production of composite osteochondral tissues were investigated using human adult adipose‐derived stem cells and polyglycolic acid (PGA) mesh scaffolds under dynamic culture conditions. For osteogenesis, cells were expanded with or without osteoinduction factors and cultured in control or osteogenic medium for 2 weeks. Osteogenic medium enhanced osteopontin and osteocalcin gene expression when applied after but not during cell expansion. Osteogenesis was induced and mineralized deposits were present in tissues produced using PGA culture in osteogenic medium. For development of osteochondral constructs, scaffolds seeded with stem cells were precultured in either chondrogenic or osteogenic medium, sutured together, and cultured in dual‐chamber stirred bioreactors containing chondrogenic and osteogenic media in separate compartments. After 2 weeks, total collagen synthesis was 2.1‐fold greater in the chondroinduced sections of the composite tissues compared with the osteoinduced sections; differentiation markers for cartilage and bone were produced in both sections of the constructs. The results from the dual‐chamber bioreactor highlight the challenges associated with achieving simultaneous chondrogenic and osteogenic differentiation in tissue engineering applications using a single stem‐cell source. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013
Determination of Heat Treatment Temperature for Completing Polycondensation of Vinyl Substituted Silica Particles Prepared by Sol‐Gel Method
Authors: Ashraf K. M. , Matsumoto S. , Kurumada K.
Published: November 2012

The completion of the polycondensation of sol‐gel derived organic‐inorganic hybrid silica by heat treatment was studied for powder samples prepared from vinyltrimethoxysilane and vinyltriethoxysilane. The appropriate temperature for the completion of the prepared submicron powdery samples from both starting compounds was determined through thermogravimetric analysis. The completion or incompletion of the polycondensation was elucidated by means of several instrumental methods in addition to a light scattering test. The lowest heat treatment conditions for the particles from vinyltrimethoxysilane and vinyltriethoxysilane are 170 °C and 180 °C, respectively, for 24 h. The morphologies of the heat treated samples were found to be slightly different depending on the starting material used.
Preparation of Agy zeolites using microwave irradiation and study on their adsorptive desulphurisation performance
Authors: Song Hua , Wan Xia , Sun Xinglong
Published: November 2012

Sorbents with Ag loading supported on NaY were synthesised by a liquid‐phase ion exchange method taking advantage of microwaves irradiation. The adsorption desulphurisation activity of the AgY adsorbent exchanged with AgNO3 solution of 0.2 mol L−1, microwave irradiation time 20 min with power 240 W as well as calcined at 500°C exhibited the best performance. Equilibrium isotherm shows that the adsorption of thiophene over the as‐prepared AgY can be represented by the Langmuir model. Kinetics of adsorptive desulphurisation followed the pesudo‐second‐order model and the equilibrium adsorption capacity q2 = 0.893 mmol g−1. © 2012 Canadian Society for Chemical Engineering
New algebraic expressions for thermodiffusion in binary n‐alkane mixtures
Authors: Srinivasan Seshasai , Saghir M. Ziad
Published: November 2012

Following a detailed analysis of the experimental data on thermodiffusion coefficients of numerous binary hydrocarbon mixtures from over 90 experiments, four new algebraic expressions are proposed. As per these formulations, the thermodiffusion coefficient of binary n‐alkane mixtures can be expressed as a function of the chemical composition of the mixture and the mixture properties such as density and viscosity. Detailed experimental validation is presented using four n‐alkane series containing a wide range of combinations of n‐alkanes. Additionally, comparison with recently proposed neural network model and a model based on the principles of non‐equilibrium thermodynamics is also presented. It has been found that the proposed algebraic models are simple in formulations, are evaluated with least computational effort and yet have a very high accuracy in predicting the thermodiffusion coefficients. © 2012 Canadian Society for Chemical Engineering
The effect of poly(ethylene‐alt‐maleic anhydride) on the reduction crystallisation behaviour of nickel powder
Authors: Bodoza T.F. , Ntuli F. , Chauke D.F. , Muzenda E.
Published: November 2012

The effect of poly(ethylene‐alt‐maleic anhydride) (EMA), an additive used in nickel powder precipitation, has been studied using sodium hypophosphite as a reducing agent. Reduction experiments were conducted using a 10 L stainless steel batch reactor. The effect of EMA was investigated by studying the evolution of the particle size distribution (PSD) and its derived moments, specific surface area, rate of reduction, pH–redox potential and elemental composition of the powder product. EMA has been found to act as a reduction catalyst and anti‐agglomerating agent. The major particulate processes identified were size dependent aggregation, molecular growth and breakage. © 2012 Canadian Society for Chemical Engineering
A quantitative analysis of branching, growth cone turning, and directed growth in zebrafish retinotectal axon guidance
Authors: Simpson Hugh D. , Kita Elizabeth M. , Scott Ethan K. , Goodhill Geoffrey J.
Published: November 2012

The topographic projection from the eye to the tectum (amphibians and fish)/superior colliculus (birds and mammals) is a paradigm model system for studying mechanisms of neural wiring development. It has previously been proposed that retinal ganglion cell axons use distinct guidance strategies in fish vs. mammals, with direct guidance to the tectal target zone in the former and overshoot followed by biased branching toward the target zone in the latter. Here we visualized individual retinal ganglion cell axons as they grew over the tectum in zebrafish for periods of 10‐21 hours and analyzed these results using an array of quantitative measures. We found that, although axons were generally guided directly toward their targets, this occurred without growth cone turning. Instead, axons branched dynamically and profusely throughout pathfinding, and successive branches oriented growth cone extension toward a target zone in a stepwise manner. These data suggest that the guidance strategies used between fish and mammals may be less distinct than previously thought. J. Comp. Neurol., 521:1409–1429, 2013. © 2012 Wiley Periodicals, Inc.
Cortical projections to the superior colliculus in tree shrews (Tupaia belangeri)
Authors: Baldwin Mary K.L. , Wei Haiyang , Reed Jamie L. , Bickford Martha E. , Petry Heywood M. , Kaas Jon H.
Published: November 2012

The visuomotor functions of the superior colliculus depend not only on direct inputs from the retina, but also on inputs from neocortex. As mammals vary in the areal organization of neocortex, and in the organization of the number of visual and visuomotor areas, patterns of corticotectal projections vary. Primates in particular have a large number of visual areas projecting to the superior colliculus. As tree shrews are close relatives of primates, and they are also highly visual, we studied the distribution of cortical neurons projecting to the superior colliculus by injecting anatomical tracers into the colliculus. Since projections from visuotopically organized visual areas are expected to match the visuotopy of the superior colliculus, injections at different retinotopic locations in the superior colliculus provide information about the locations and organization of topographic areas in extrastriate cortex. Small injections in the superior colliculus labeled neurons in locations within areas 17 (V1) and 18 (V2) that are consistent with the known topography of these areas and the superior colliculus. In addition, the separate locations of clusters of labeled cells in temporal visual cortex provide evidence for five or more topographically organized areas. Injections that included deeper layers of the superior colliculus also labeled neurons in medial frontal cortex, likely in premotor cortex. Only occasional labeled neurons were observed in somatosensory or auditory cortex. Regardless of tracer injection location, we found that, unlike primates, a substantial projection to the superior colliculus from posterior parietal cortex is not a characteristic of tree shrews. J. Comp. Neurol. 521:1614–1632, 2013. © 2012 Wiley Periodicals, Inc.
Projections of the superior colliculus to the pulvinar in prosimian galagos (Otolemur garnettii) and VGLUT2 staining of the visual pulvinar
Authors: Baldwin Mary K.L. , Balaram Pooja , Kaas Jon H.
Published: November 2012

An understanding of the organization of the pulvinar complex in prosimian primates has been somewhat elusive due to the lack of clear architectonic divisions. In the current study we reveal features of the organization of the pulvinar complex in galagos by examining superior colliculus (SC) projections to this structure and comparing them with staining patterns of the vesicular glutamate transporter, VGLUT2. Cholera toxin subunit β (CTB), Fluoro‐ruby (FR), and wheat germ agglutinin conjugated with horseradish peroxidase (WGA‐HRP) were placed in topographically different locations within the SC. Our results showed multiple topographically organized patterns of projections from the SC to several divisions of the pulvinar complex. At least two topographically distributed projections were found within the lateral region of the pulvinar complex, and two less obvious topographical projection patterns were found within the caudomedial region, in zones that stain darkly for VGLUT2. The results, considered in relation to recent observations in tree shrews and squirrels, suggest that parts of the organizational scheme of the pulvinar complex in primates are present in rodents and other mammals. J. Comp. Neurol. 521:1664–1682, 2013. © 2012 Wiley Periodicals, Inc.
Laminar segregation of GABAergic neurons in the avian nucleus isthmi pars magnocellularis: A retrograde tracer and comparative study
Authors: Faunes Macarena , Fernández Sara , Gutiérrez‐Ibáñez Cristián , Iwaniuk Andrew N. , Wylie Douglas R. , Mpodozis Jorge , Karten Harvey J. , Marín Gonzalo
Published: November 2012

The isthmic complex is part of a visual midbrain circuit thought to be involved in stimulus selection and spatial attention. In birds, this circuit is composed of the nuclei isthmi pars magnocellularis (Imc), pars parvocellularis (Ipc), and pars semilunaris (SLu), all of them reciprocally connected to the ipsilateral optic tectum (TeO). The Imc conveys heterotopic inhibition to the TeO, Ipc, and SLu via widespread γ‐aminobutyric acid (GABA)ergic axons that allow global competitive interactions among simultaneous sensory inputs. Anatomical studies in the chick have described a cytoarchitectonically uniform Imc nucleus containing two intermingled cell types: one projecting to the Ipc and SLu and the other to the TeO. Here we report that in passerine species, the Imc is segregated into an internal division displaying larger, sparsely distributed cells, and an external division displaying smaller, more densely packed cells. In vivo and in vitro injections of neural tracers in the TeO and the Ipc of the zebra finch demonstrated that neurons from the external and internal subdivisions project to the Ipc and the TeO, respectively, indicating that each Imc subdivision contains one of the two cell types hodologically defined in the chick. In an extensive survey across avian orders, we found that, in addition to passerines, only species of Piciformes and Rallidae exhibited a segregated Imc, whereas all other groups exhibited a uniform Imc. These results offer a comparative basis to investigate the functional role played by each Imc neural type in the competitive interactions mediated by this nucleus. J. Comp. Neurol. 521:1727–1742, 2013. © 2012 Wiley Periodicals, Inc.
Commissural axons of the mouse cochlear nucleus
Authors: Brown M. Christian , Drottar Marie , Benson Thane E. , Darrow Keith
Published: November 2012

The axons of commissural neurons that project from one cochlear nucleus to the other were studied after labeling with anterograde tracer. Injections were made into the dorsal subdivision of the cochlear nucleus in order to restrict labeling only to the group of commissural neurons that gave off collaterals to, or were located in, this subdivision. The number of labeled commissural axons in each injection was correlated with the number of labeled radiate multipolar neurons, suggesting radiate neurons as the predominant origin of the axons. The radiate commissural axons are thick and myelinated, and they exit the dorsal acoustic stria of the injected cochlear nucleus to cross the brainstem in the dorsal half, near the crossing position of the olivocochlear bundle. They enter the opposite cochlear nucleus via the dorsal and ventral acoustic stria and at its medial border. Reconstructions of single axons demonstrate that terminations are mostly in the core and typically within a single subdivision of the cochlear nucleus. Extents of termination range from narrow to broad along both the dorsoventral (i.e., tonotopic) and the rostrocaudal dimensions. In the electron microscope, labeled swellings form synapses that are symmetric (in that there is little postsynaptic density), a characteristic of inhibitory synapses. Our labeled axons do not appear to include excitatory commissural axons that end in edge regions of the nucleus. Radiate commissural axons could mediate the broadband inhibition observed in responses to contralateral sound, and they may balance input from the two ears with a quick time course. J. Comp. Neurol. 521:1683–1696, 2013. © 2012 Wiley Periodicals, Inc.
Lipid oxidation products of heated soybeans as a possible cause of protection from ruminal biohydrogenation
Authors: Kaleem Muhammad , Farizon Yves , Enjalbert Francis , Troegeler‐Meynadier Annabelle
Published: November 2012

Heating oilseeds has been shown to improve the milk fatty acid profile when given to dairy cows, compared to raw oilseeds. However, results from published studies are conflicting. The conditions of heating and storage of the oilseeds could be responsible for these differences, probably partly through their effects on lipid oxidation, the products of which could act on ruminal biohydrogenation (BH). Thus, 15 different treatments were applied to ground soybeans: three levels of heating (no heating, 30 min at 110 or 150°C) × 5 ambient storage durations (0, 1, 2, 4, or 6 months). Soybeans were incubated in vitro with ruminal fluid for 6 h. Triacylglycerol (TAG) polymers, hydroperoxides and hydroxyacids (HOA), aldehydes, and fatty acids were assayed in soybeans and ruminal culture. No TAG polymer was detected in any treatment. Soybeans stored for a long time had a high content of HOA, whereas those heated at 150°C, whatever the storage duration, had high aldehyde contents. The percentage disappearance of cis‐9,cis‐12 18:2 and cis‐9,cis‐12,cis‐15 18:3 in incubates decreased significantly in cultures with heated soybeans, especially at 150°C, suggesting that this partial protection of polyunsaturated fatty acids (PUFA) from BH was at least in part linked to the aldehyde content of the heated soybeans.

Practical applications: Oilseeds given to ruminants are often heated, and heat treatment is known to generate oxidation products. Knowing what oxidation products influence ruminal biohydrogenation of unsaturated fatty acids could result in technological processes allowing a better transfer of unsaturated fatty acids from oilseeds to ruminant products.
Bedforms: views and new perspectives from the third international workshop on Marine and River Dune Dynamics (MARID3)
Authors: Parsons Daniel R. , Best Jim
Published: November 2012

This Commentary introduces a Special Issue of Earth Surface Processes and Landforms dedicated to the memory of Stephen Coleman (1966–2012) who sadly passed away on July 23, 2012. Stephen was an incredible enthusiast for the study of bedforms and made seminal contributions to our knowledge and understanding of flow, sediment transport and bedform dynamics. Stephen presented a keynote address at MARID 3, which has led to this Special Issue (see Coleman SE, Nikora VI. 2011. Fluvial dunes: initiation, characterization, flow structure. Earth Surface Processes and Landforms 36: 39–57. DOI. 10.1002/esp.2096) and was always keen to discuss research, from theory to techniques to experiments. He was always generous with his time and touched many with the influence of his thoughts and intellect. Our community has lost an outstanding scientist and Stephen will be greatly missed by us all. Copyright © 2012 John Wiley & Sons, Ltd.