bluuebunny/crossref_metadata_2025_split huggingface dataset:
“Ménage à trois”: the presence/absence of thyme shapes the mutualistic interaction between the host plant Medicago truncatula (Fabaceae) and its symbiotic bacterium Sinorhizobium meliloti
Authors: Ehlers Bodil K. , Grøndahl Eva , Ronfort Joëlle , Bataillon Thomas 
Published: June 2012

AbstractThe long‐term maintenance of specialized mutualisms remains an evolutionary puzzle. Recent focus has been on factors governing the stability of these mutualisms, including sanctions by the host, partner choice, and coevolutionary constraint, that is, the genetic correlation (rG) between fitness of both partners. So far these studies have been typically carried out in a single environment. Here, we ask if the genetic correlation between fitness of the host plant Medicago truncatula (Fabaceae) and its bacterial symbiont Sinorhizobium meliloti is affected by the presence/absence of a monoterpene (carvacrol) leached into the soil by Thymus vulgaris—a common plant of the Mediterranean vegetation, often co‐occuring with Medicago. We show that the presence of carvacrol in the soil dramatically affects fitness of the rhizobial partner and increases the magnitude of rG between plant and rhizobia fitness (rG= 0.02 ± 0.05 vs. rG= 0.57 ± 0.02). This finding emphasizes the importance of heterogeneity in the biotic environment for understanding the evolution of species interactions.
Interfamily variation in amphibian early life‐history traits: raw material for natural selection?
Authors: Hopkins Gareth R. , Gall Brian G. , French Susannah S. , Brodie Edmund D. 
Published: June 2012

AbstractThe embryonic development and time to hatching of eggs can be highly adaptive in some species, and thus under selective pressure. In this study, we examined the underlying interfamily variation in hatching timing and embryonic development in a population of an oviparous amphibian, the rough‐skinned newt (Taricha granulosa). We found significant, high variability in degree of embryonic development and hatching timing among eggs from different females. Patterns of variation were present regardless of temperature. We also could not explain the differences among families by morphological traits of the females or their eggs. This study suggests that the variation necessary for natural selection to act upon is present in the early life history of this amphibian.
Phytosterols in pumpkin seed oil extracted by organic solvents and supercritical CO2
Authors: Hrabovski Nataša , Sinadinović‐Fišer Snežana , Nikolovski Branislava , Sovilj Milan , Borota Olga 
Published: June 2012

AbstractPhytosterols in Cucurbita pepo convar. citrullina seed oil were analyzed by GC–MS after extraction by the organic solvents, hexane and petroleum ether, and by supercritical carbon dioxide at 400 bar and 40°C. Desmosterol, campesterol, stigmasterol, β‐sitosterol, spinasterol, Δ7,22,25‐stigmastatrienol, Δ7‐stigmastenol, Δ7,25‐stigmastadienol, and Δ7‐avenasterol were identified mass spectrometrically via detection of the parent molecular ions and fragmentation patterns of corresponding trimethylsilyl derivatives. The used derivatizing agents N‐methyl‐N‐(trimethylsilyl)trifluoroacetamide (MSTFA) and N,O‐bis(trimethylsilyl)trifluoroacetamide (BSTFA) are equally effective for phytosterol content determination. As expected, the predominant phytosterols were Δ7‐sterols that ranged from 91.0 to 94.2% of the total phytosterol content given as sum of free sterols and steryl esters. Comparison of extraction methods revealed that, although the oil yields obtained by extraction with hexane, petroleum ether and supercritical CO2 were 43.37, 44.65, and 36.17%, respectively, the total phytosterol content in supercritical CO2 extract (294 mg/100 g oil, for both MSTFA and BSTFA) was about 30% higher than in hexane and about 20% higher than in petroleum ether extract.Practical applications: Extraction with the application of fluids in supercritical state opens a new approach to the production of edible vegetable oils. Many economical, health, and environmental aspects are interlaced in this modern approach. By applying the supercritical extraction, the selectivity of the extraction can be significantly improved compared to traditional methods of extraction. Thus, depending on the operating conditions of supercritical CO2 extraction higher total phytosterol content can be achieved resulting in improved nutritional value of the pumpkin seed oil.
Soybean oil‐based polyurethane networks as candidate biomaterials: Synthesis and biocompatibility
Authors: Miao Shida , Sun Lijing , Wang Ping , Liu Ruina , Su Zhiguo , Zhang Songping 
Published: June 2012

AbstractBiobased polymeric materials are gaining increasing attention in biomedical areas. Here, we report a new class of biocompatible polyurethanes prepared from soybean oil‐based polyol that was synthesized by ring‐opening reaction of epoxidized monoglyceride (EMG) with lactic acid. By adjusting the molar ratio of hydroxyl to isocyanate group and the content of chain extender, soybean oil‐based polyurethanes with tensile strength of 9.30–27.1 MPa and elongation at break of 74.1–110.7% were prepared, while usual lipid‐based polyurethanes with the same 1,6‐diisocyanatohexane as reactant hardly have tensile strength higher than 5 MPa. Mouse fibroblast cells (L‐929) showed good adhesion and growth behavior on the polyurethane samples with more hydrophilic surfaces, and the cell viabilities of more than 50% were achieved with commercial tissue culture polystyrene (TCPS) disk as control. The good mechanical property and biocompatibility of the soybean oil‐based polyurethanes will make them suitable for wide range of potential biomedical applications.Practical applications: The synthesized soybean oil‐based polyurethanes have adjustable tensile strengths from 9.30–27.1 MPa and elongation at break of 74.1–110.7%. Along with their good biocompatibility, the polyurethanes can potentially replace wide range of part of petroleum‐based polymeric materials, particularly as biomedical materials.
Synthesis of a Naphthalene‐diimide Cyclophane for Tuning Supramolecular Interactions by Metal Ions
Authors: Yu Yanwen , Li Yongjun , Chen Songhua , Liu Taifeng , Qin Zhihong , Liu Huibiao , Li Yuliang 
Published: June 2012

AbstractA new supramolecular species of naphthalene‐diimide cyclophane containing triazole units was synthesized, and its fluorescent responses to metal ions were investigated in dichloromethane (DCM). The fluorescence emission of NDI was quenched by intramolecular electron transfer, whereas the appearance of dimer emission of the naphthalene‐diimide in the presence of Mg2+, Ba2+, Hg2+, Ca2+, Zn2+ and Pb2+ was observed.
Synthesis of 2,6‐Bis(oxazolyl)pyridine Ligands for Luminescent LnIII Complexes
Authors: Pereira Goreti , Ferreira Miguel F. , Castanheira Elisabete M. S. , Martins José A. , Ferreira Paula M. T. 
Published: June 2012

AbstractNew bis(oxazolyl)pyridine ligands for LnIII ions were prepared by using an expeditious methodology from threonine and dipicolinic chloride. The synthetic strategy includes a dehydration step to give a bis(dehydroaminobutyric acid) derivative followed by bromination and cyclization with DBU. Photophysical studies of EuIII and TbIII complexes of these ligands showed that the 2,6‐bis(oxazolyl)pyridine moiety acts as an effective sensitizer for lanthanide luminescence and indicate the formation of 3:1 complexes [Ln{bis(oxazole)pyridine}3]3+.
Analysis of the Electrochemical Oxidation of Multiwalled Carbon Nanotube Tower Electrodes in Sodium Hydroxide
Authors: Doepke Amos , Han Changseok , Back Tyson , Cho Wondong , Dionysiou Dionysios D. , Shanov Vesselin , Halsall H. Brian , Heineman William R. 
Published: June 2012

AbstractTowers of aligned multiwalled carbon nanotubes (MWCNTs) were electrochemically oxidized in aqueous 1 M NaOH. An oxidation current that decayed with time was monitored using amperometry at a fixed potential. Cyclic voltammetry showed that the background current and electrode capacitance increased after oxidation without significantly affecting the faradaic current from the reduction of ferricyanide. Oxidation in NaOH caused morphological changes and increased hydrophilicity of the MWCNT tower electrodes. XPS spectra indicated increased oxygen on the surface after oxidation, while Raman spectra indicated that a large amount of amorphous carbon was present before and after oxidation.
Relationships between the Seasonal Variations of Macroinvertebrates, and Land Uses for Biomonitoring in the Xitiaoxi River Watershed, China
Authors: Zhang Yong , Wang Beixin , Han Minghua , Wang Lizhu 
Published: June 2012

AbstractThe impacts of differences in watershed land uses, and differences in seasonality on benthic macroinvertebrate communities, were evaluated in 12 stream sites within the Xitiaoxi River watershed, China, from April 2009 to January 2010. The composition of macroinvertebrate community differed significantly among three land use types. Forested sites were characterized by high taxa richness, diversity and the benthic‐index of biotic integrity (B‐IBI), while farmland and urban disturbed stream sites presented contrary patterns. The percentage of urban land use, conductivity, dissolved oxygen, ammonia nitrogen and total phosphorus were the major drivers for the variations. The land use related water quality stress gradients of the four sampling seasons were determined by means of four independent Principal Component Analyses. The responses of macroinvertebrate community metrics, to anthropogenic stressors, were explored using Spearman Rank Correlation analyses. All the selected metrics, including total numbers of taxa, numbers of Ephemeroptera, Plecoptera and Trichoptera taxa, percentage of non‐insect abundance, percentage of scrapers abundance, Pielou’s evenness index, Simpson diversity index, and the Benthic Index of Biotic Integrity were correlated significantly with environmental gradients (PC1) in autumn. In other seasons such correlations were less pronounced. Our results imply that autumn is the optimal time to sample macroinvertebrate communities, and to conduct water quality biomonitoring in this subtropical watershed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Glucose‐6‐phosphate metabolism in Plasmodium falciparum
Authors: Preuss Janina , Jortzik Esther , Becker Katja 
Published: June 2012

AbstractMalaria is still one of the most threatening diseases worldwide. The high drug resistance rates of malarial parasites make its eradication difficult and furthermore necessitate the development of new antimalarial drugs. Plasmodium falciparum is responsible for severe malaria and therefore of special interest with regard to drug development. Plasmodium parasites are highly dependent on glucose and very sensitive to oxidative stress; two observations that drew interest to the pentose phosphate pathway (PPP) with its key enzyme glucose‐6‐phosphate dehydrogenase (G6PD). A central position of the PPP for malaria parasites is supported by the fact that human G6PD deficiency protects to a certain degree from malaria infections. Plasmodium parasites and the human host possess a complete PPP, both of which seem to be important for the parasites. Interestingly, there are major differences between parasite and human G6PD, making the enzyme of Plasmodium a promising target for antimalarial drug design. This review gives an overview of the current state of research on glucose‐6‐phosphate metabolism in P. falciparum and its impact on malaria infections. Moreover, the unique characteristics of the enzyme G6PD in P. falciparum are discussed, upon which its current status as promising target for drug development is based. © 2012 IUBMB IUBMB Life, 64(7): 603–611, 2012
Lyase activity of glycogen synthase: Is an elimination/addition mechanism a possible reaction pathway for retaining glycosyltransferases?
Authors: Díaz Adelaida , Díaz‐Lobo Mireia , Grados Enrique , Guinovart Joan J. , Fita Ignacio , Ferrer Joan C. 
Published: June 2012

AbstractDespite the biological relevance of glycosyltrasferases (GTs) and the many efforts devoted to this subject, the catalytic mechanism through which a subclass of this large family of enzymes, namely those that operate with net retention of the anomeric configuration, has not been fully established. Here, we show that in the absence of an acceptor, an archetypal retaining GT such as Pyrococcus abyssi glycogen synthase (PaGS) reacts with its glucosyl donor substrate, uridine 5'‐diphosphoglucose (UDP‐Glc), to produce the scission of the covalent bond between the terminal phosphate oxygen of UDP and the sugar ring. X‐ray diffraction analysis of the PaGS/UDP‐Glc complex shows no electronic density attributable to the UDP moiety, but establishes the presence in the active site of the enzyme of a glucose‐like derivative that lacks the exocyclic oxygen attached to the anomeric carbon. Chemical derivatization followed by gas chromatography/mass spectrometry of the isolated glucose‐like species allowed us to identify the molecule found in the catalytic site of PaGS as 1,5‐anhydro‐D‐arabino‐hex‐1‐enitol (AA) or its tautomeric form, 1,5‐anhydro‐D‐fructose. These findings are consistent with a stepwise SNi‐like mechanism as the modus operandi of retaining GTs, a mechanism that involves the discrete existence of an oxocarbenium intermediate. Even in the absence of a glucosyl acceptor, glycogen synthase (GS) promotes the formation of the cationic intermediate, which, by eliminating the proton of the adjacent C2 carbon atom, yields AA. Alternatively, these observations could be interpreted assuming that AA is a true intermediate in the reaction pathway of GS and that this enzyme operates through an elimination/addition mechanism. © 2012 IUBMB Life, 64(7): 649–658, 2012.
Application of Graphene as a Sorbent for Simultaneous Preconcentration and Determination of Trace Amounts of Cobalt and Nickel in Environmental Water and Vegetable Samples
Authors: Wang Yu‐Kun , Gao Shu‐Tao , Ma Jing‐Jun , Li Jing‐Ci 
Published: June 2012

AbstractA new method using a column packed with graphene as adsorbent was developed for the preconcentration of trace amounts of cobalt (Co) and nickel (Ni) prior to their determinations by flame atomic absorption spectrometry. Several factors influencing the extraction efficiency of Co and Ni and their subsequent determinations, such as pH, amounts of the chelating agent, flow rates of sample and eluent solution, eluent type and its volume, breakthrough volume, and adsorption capacity were established. Under the optimum conditions, the calibration graphs were linear in the range of 4.0‐200.0 μg L−1 and 5.0‐200.0 μg L−1 with detection limits of 0.36 μg L−1 and 0.51 μg L−1 for Co and Ni, respectively. Good relative standard deviations for ten determinations of 100.0 μg L−1 of Co and Ni were 3.2 and 3.6%, respectively. The results for determination of Co and Ni in tap water, river water, sea water, vegetable and spiked samples have demonstrated the accuracy and applicability of the proposed method. To validate the proposed method, three certified reference materials of environment water (GSBZ 50030‐94 and GSB 07‐1186‐2000) and tomato leaf (GSBZ 51001‐94) were analyzed, and the determined values were in good agreement with the certified values.
Germline stem cell lineage tracing by free‐floating immunofluorescent assay of mouse seminiferous tubule
Authors: Jin Bo , Guo Bin , Che Guanyu , Sun Yixue , Liu Yang , Zhang Xueming 
Published: June 2012

AbstractWhole‐mount immunohistochemistry (whole‐mount IH) of the seminiferous tubule is widely used to investigate the self‐renewal and differentiation of spermatogonial stem cells (SSCs). Examination of the length of spermatogonial cysts is critical for tracing SSCs lineage by using Whole‐mount IH. However, it is difficult for antibody molecules to penetrate into the depth of seminiferous epithelium because its thickness and the tight peritubular myoid and basement membrane outside. Here, we developed a free‐floating immunofluorescent procedure of mouse seminiferous tubules using regular incubation time and normal antibody concentration. Microscopic results showed that undifferentiated spermatogonia were positively labeled by promyelocytic leukemia zinc finger protein, E‐cadherin, and glial cell line‐derived neurotrophic factor family receptor alpha 1, respectively. Spermatogonial cysts in varied length were revealed clearly and spermatogonia subpopulations including Asingle(As), Apaired(Apr), and Aaligned(Aal) were distinguished in lower background images. This method provides us an alternate simple way to trace the lineage of individual SSCs and show their three‐dimensional locations and distributions within their niches anatomically in next step. Microsc. Res. Tech. 75:1150–1153, 2012. © 2012 Wiley Periodicals, Inc.
Effective, safe nonviral gene transfer to preserve the chondrogenic differentiation potential of human mesenchymal stem cells
Authors: Elsler Sebastian , Schetting Sarah , Schmitt Gertrud , Kohn Dieter , Madry Henning , Cucchiarini Magali 
Published: June 2012

AbstractBackgroundGenetic modification of mesenchymal stem cells (MSCs) comprises a promising tool to generate cell‐ and gene‐based platforms for regenerative approaches of articular cartilage repair. In the present study, we systematically screened a panel of 15 nonviral compounds for their ability to promote safe, efficient and durable gene expression in human bone marrow‐derived MSCs (hMSCS) without impeding their commitment towards chondrogenic differentiation.MethodsPrimary hMSCs were transfected with plasmid vectors carrying sequences for the Photinus pyralis luciferase Escherichia coli β‐galactosidase, or human insulin‐like growth factor I via 15 nonviral formulations. Transgene expression and transfection efficiencies were monitored for each component in parallel with the effects on cell viability and cytotoxicity. Upon optimization, the most promising reagent was then evaluated for a possible influence on the chondrogenic potential of hMSCs.ResultsAmong all formulations tested, GeneJammer® gave the best results for transgene expression and transfection efficacy (25–14% from days 2–21 in monolayer cultures and 35% in 21‐day aggregate cultures), allowing for high levels of viability (92–94%) and modest cytotoxicity (< 12%). Most notably, the application of this reagent did not affect the potential of the cells for chondrogenic differentiation when maintained in long‐term (21 days) three‐dimensional (aggregate) cultures.ConclusionsThe data indicate that safe, efficient transgene expression can be achieved in hMSCs over time using the nonviral GeneJammer® compound, showing promise for future therapeutic settings aiming to treat human articular cartilage disorders. Copyright © 2012 John Wiley & Sons, Ltd.
The spinal cord supports of vertebrae in the crown‐group salamanders (Caudata, Urodela)
Authors: Skutschas Pavel P. , Baleeva Nataly V. 
Published: June 2012

AbstractThe development of spinal cord supports (bony thickenings which extend into the vertebral canal of vertebrae) in primitive (Salamandrella keyserlingii) and derived (Lissotriton vulgaris) salamanders were described. The spinal cord supports develop as the protuberances of periostal bone of the neural arches in the anteroproximal part of the septal collagenous fibers which connect a transverse myoseptum with the notochord and spinal cord, in the septal bundle inside the vertebral canal. Spinal cord supports were also found in some teleostean (Salmo salar, Oncorhynchus mykiss) and dipnoan (Protopterus sp.) fishes. The absence of the spinal cord supports in vertebrates with cartilaginous vertebrae (lampreys, chondrichthyan, and chondrostean fishes) corresponds to the fact that the spinal cord supports are bone structures. The absence of the spinal cord supports in frogs correlates with the lack of the well developed septal bundles inside the vertebral canal. The spinal cord supports are, presumably, a synapomorphic character for salamanders which originated independently of those observed in teleostean and dipnoan fishes. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.
Comparative anatomy of slime glands in onychophora (velvet worms)
Authors: Baer Alexander , Mayer Georg 
Published: June 2012

AbstractOnychophorans use a unique hunting and defense strategy, which involves the ejection of an adhesive slime secretion produced by a pair of specialized glands. So far, a comparative study on the anatomy of these glands has not been carried out among different species. In this article, we compare anatomical features of slime glands in representatives of two major onychophoran subgroups, the Peripatopsidae and the Peripatidae, from different parts of the world. Our data show that the musculature of the reservoir is conserved whereas the composition of the secretory duct displays taxon‐specific variation. Major differences concern the arrangement of glandular endpieces, which are distributed along the duct in Peripatopsidae but condensed in numerous repeated rosettes in Peripatidae. In addition, there are differences in the attachment pattern of slime glands to the inner surface of the body wall and to the outer surface of the gut between the two major onychophoran subgroups. A tube‐like structure with a putative valve‐like function is found at the transition of the secretory duct and the reservoir in the five Peripatopsidae species studied whereas it is absent in the two representatives of Peripatidae. Our findings suggest that the arrangement of musculature in the reservoir of the slime gland has remained unchanged since the divergence of Peripatidae and Peripatopsidae, while the composition of the secretory duct has been altered in one of these groups. However, the direction of evolutionary changes in duct composition cannot be determined unambiguously due to current uncertainty regarding the phylogenetic relationships of Onychophora. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.
Behavioural modelling of amplifier asymmetry in the time domain
Authors: Jang W. , Kriplani N. M. , Steer M. B. 
Published: June 2012

SUMMARYPower amplifier asymmetry is captured by a behavioural model that contains multiple slices representing the amplifier's nonlinearity and long‐term, that is low frequency, memory. The simulation is performed entirely in the time domain, and the expense associated with performing a purely transient radio frequency (RF) simulation is circumvented by scaling down the carrier frequency by two orders of magnitude. This leads to a manageable transient simulation with results scaling back to the original carrier frequency. The model is empirical and can be easily implemented in any general purpose circuit simulation environment. The baseband portion of the model parameters was extracted and the simulation result was compared with measurement, thereby demonstrating that a nonlinear and accurate transient analysis routine can be effectively employed to capture memory‐related RF power amplifier phenomena. Copyright © 2012 John Wiley & Sons, Ltd.
GPU‐based acceleration of computational electromagnetics codes
Authors: Donno Danilo De , Esposito Alessandra , Monti Giuseppina , Catarinucci Luca , Tarricone Luciano 
Published: June 2012

SUMMARYThe solution of large and complex electromagnetic (EM) problems often leads to a substantial demand for high‐performance computing resources and strategies. This is true for a wide variety of numerical methods and applications, ranging from EM compatibility to radio‐coverage, circuit modeling, and optimization of components. In the last decades, graphics processing units (GPUs) have gained popularity in scientific computing as a low‐cost and powerful parallel architecture. This paper gives an overview of the main efforts of researchers to port computational electromagnetics (CEM) codes to GPU. Moreover, GPU implementation aspects of two well‐known techniques, namely the finite‐difference time domain (FDTD) and the method of moments (MoM), are investigated. The impressive speed‐ups achieved (up to 60× and 25× for FDTD and MoM, respectively) demonstrate the effectiveness of GPUs in accelerating CEM codes. Copyright © 2012 John Wiley & Sons, Ltd.