Effect of solid freeform fabrication-based polycaprolactone/poly(lactic-co-glycolic acid)/collagen scaffolds on cellular activities of human adipose-derived stem cells and rat primary hepatocytes

Highly biocompatible polycaprolactone (PCL)/poly(lactic-co-glycolic acid) (PLGA)/collagen scaffolds in which the PCL/PLGA collagen solution was selectively dispensed into every other space between the struts were fabricated using solid freeform fabrication (SFF) technology, as we described previously. The objective of this study was to evaluate and compare the PCL/PLGA/collagen scaffolds (group 3) with PCL/PLGA-only scaffolds (group 1) and PCL/PLGA scaffolds with collagen by the dip-coating method (group 2) using human adipose-derived stem cells (hASCs) and rat primary hepatocytes. The selectively dispensed collagen formed a three-dimensional (3D) network of nanofibers in group 3, as observed by scanning electron microscopy. The compressive strength and modulus of group 3 were approximately 140 and 510 times higher, respectively, than those of a sponge-type collagen scaffold whose weak mechanical properties were regarded as a critical drawback. Proliferation and osteogenic differentiation of hASCs were promoted significantly in group 3 compared to groups 1 and 2. In addition, we found that the viability and albumin secretion ability of rat primary hepatocytes were highly retained for 10 days in group 3 but not group 1. Interestingly, hepatocyte aggregation, which enhances hepatic function through cell-cell interactions, was observed particularly in group 3. In conclusion, group 3, in which the collagen was selectively dispensed in the 3D space of the porous PCL/PLGA framework, will be a promising 3D scaffold for culturing various cell types.

Stimulation of healing within a rabbit calvarial defect by a PCL/PLGA scaffold blended with TCP using solid freeform fabrication technology

The purpose of this study was to investigate the healing capacity within an 8-mm rabbit calvarial defect using a polycaprolactone (PCL)/poly(lactic-co-glycolic acid) (PLGA) scaffold blended with tri-calcium phosphate (TCP) that was constructed using solid freeform fabrication (SFF) technology. The PCL/PLGA/TCP scaffold showed a 37 % higher compressive strength and rougher surface than the PCL/PLGA scaffold. In animal experiments, new bone formation was analyzed using microcomputed tomography (micro-CT) and histological and histometric analyses. The PCL/PLGA/TCP groups had significantly greater neo-tissue areas as compared with the control groups at 4 and 8 weeks (P < 0.05). The PCL/PLGA/TCP group had significantly greater bone density as compared with the control and PCL/PLGA groups at 4 and 8 weeks (P < 0.005). The results of this study suggest that the PCL/PLGA/TCP scaffold fabricated using SFF technology is useful for recovering and enhancing new bone formation in bony defects in rabbits.

Fabrication of blended polycaprolactone/poly(lactic-co-glycolic acid)/β-tricalcium phosphate thin membrane using solid freeform fabrication technology for guided bone regeneration

This study developed a bioabsorbable-guided bone regeneration membrane made of blended polycaprolactone (PCL), poly(lactic-co-glycolic acid) (PLGA), and beta-tricalcium phosphate (β-TCP) using solid freeform fabrication (SFF) technology. The chemical and physical properties of the membrane were evaluated using field emission scanning electron microscopy, energy dispersive spectroscopy, and a tensile test. In vitro cell activity assays revealed that the adhesion, proliferation, and osteogenic differentiation of seeded adipose-derived stem cells (ADSCs) were significantly promoted by the PCL/PLGA/β-TCP membranes compared with PCL/PLGA membranes. When the PCL/PLGA and PCL/PLGA/β-TCP membranes were implanted on rabbit calvaria bone defects without ADSCs, microcomputed tomography and histological analyses confirmed that the SFF-based PCL/PLGA/β-TCP membranes greatly increased bone formation without the need for bone substitute materials. Moreover, tight integration, which helps to prevent exposure of the membrane, between both membranes and the soft tissues was clearly observed histologically. The SFF-based PCL/PLGA and PCL/PLGA/β-TCP membranes retained their mechanical stability for up to 8 weeks without significant collapse. Furthermore, PCL/PLGA/β-TCP underwent adequate degradation without a significant immune response at 8 weeks.

Decoherence window and electron-nuclear cross relaxation in the molecular magnet V15

Rabi oscillations in the V(15) single molecule magnet embedded in the surfactant (CH(3))(2)[CH(3)(CH(2))(16)CH(2)](2)N(+) have been studied at different microwave powers. An intense damping peak is observed when the Rabi frequency Ω(R) falls in the vicinity of the Larmor frequency of protons ω(N). The experiments are interpreted by a model showing that the damping (or Rabi) time τ(R) is directly associated with decoherence caused by electron-nuclear cross relaxation in the rotating reference frame. This decoherence induces energy dissipation in the range ω(N) - σ(e) < Ω(R) < ω(N), where σ(e) is the mean superhyperfine field induced by protons at V(15). Weaker decoherence without dissipation takes place outside this window. Specific estimations suggest that this rapid cross relaxation in a resonant microwave field, observed for the first time in V(15), should also take place, e.g., in Fe(8) and Mn(12).

Effect of pore architecture and stacking direction on mechanical properties of solid freeform fabrication-based scaffold for bone tissue engineering

Fabrication of a three-dimensional (3D) scaffold with increased mechanical strength may be an essential requirement for more advanced bone tissue engineering scaffolds. Various material- and chemical-based approaches have been explored to enhance the mechanical properties of engineered bone tissue scaffolds. In this study, the effects of pore architecture and stacking direction on the mechanical and cell proliferation properties of a scaffold were investigated. The 3D scaffold was prepared using solid freeform fabrication technology with a multihead deposition system. Various types of scaffolds with different pore architectures (lattice, stagger, and triangle types) and stacking directions (horizontal and vertical directions) were fabricated with a blend of polycaprolactone and poly lactic-co-glycolic acid. In compression tests, the triangle-type scaffold was the strongest among the experimental groups. Stacking direction affected the mechanical properties of scaffolds. An in vitro cell counting kit-8 assay showed no significant differences in optical density depending on the different pore architectures and stacking directions. In conclusion, mechanical properties of scaffolds can be enhanced by controlling pore architecture and stacking direction.

Temperature-dependent Fermi surface evolution in heavy fermion CeIrIn5

We address theoretically the evolution of the heavy fermion Fermi surface (FS) as a function of temperature (T), using a first principles dynamical mean-field theory approach combined with density functional theory. We focus on the archetypical heavy electrons in CeIrIn{5}. Upon cooling, both the quantum oscillation frequencies and cyclotron masses show logarithmic scaling behavior [∼ln(T{0}/T)] with different characteristic temperatures T{0}=130 and 50 K, respectively. The enlargement of the electron FSs at low T is accompanied by topological changes around T=10-50  K. The resistivity coherence peak observed at T≃50  K is the result of the competition between the binding of incoherent 4f electrons to the spd conduction electrons at Fermi level (E{F}) and the formation of coherent 4f electrons.

Anisotropic Dirac fermions in a Bi square net of SrMnBi2

We report the observation of highly anisotropic Dirac fermions in a Bi square net of SrMnBi(2), based on a first-principles calculation, angle-resolved photoemission spectroscopy, and quantum oscillations for high-quality single crystals. We found that the Dirac dispersion is generally induced in the (SrBi)(+) layer containing a double-sized Bi square net. In contrast to the commonly observed isotropic Dirac cone, the Dirac cone in SrMnBi(2) is highly anisotropic with a large momentum-dependent disparity of Fermi velocities of ~8. These findings demonstrate that a Bi square net, a common building block of various layered pnictides, provides a new platform that hosts highly anisotropic Dirac fermions.

Development of a hybrid scaffold with synthetic biomaterials and hydrogel using solid freeform fabrication technology

Natural biomaterials such as hyaluronic acid, gelatin and collagen provide excellent environments for tissue regeneration. Furthermore, gel-state natural biomaterials are advantageous for encapsulating cells and growth factors. In cell printing technology, hydrogel which contains cells was printed directly to form three-dimensional (3D) structures for tissue or organ regeneration using various types of printers. However, maintaining the 3D shape of the printed structure, which is made only of the hydrogel, is very difficult due to its weak mechanical properties. In this study, we developed a hybrid scaffold consisting of synthetic biomaterials and natural hydrogel using a multi-head deposition system, which is useful in solid freeform fabrication technology. The hydrogel was intentionally infused into the space between the lines of a synthetic biomaterial-based scaffold. The cellular efficacy of the hybrid scaffold was validated using rat primary hepatocytes and a mouse pre-osteoblast MC3T3-E1 cell line. In addition, the collagen hydrogel, which encapsulates cells, was dispensed and the viability of the cells observed. We demonstrated superior effects of the hybrid scaffold on cell adhesion and proliferation and showed the high viability of dispensed cells.

Synchrotron X-ray bioimaging of bone regeneration by artificial bone substitute of MegaGen Synthetic Bone and hyaluronate hydrogels

Synchrotron X-ray bioimaging was successfully carried out to observe bone regeneration by a novel artificial bone substitute of bioactive MegaGen Synthetic Bone (MGSB) and hyaluronate (HA) hydrogels. A biphasic calcium phosphate of MGSB was prepared by chemical precipitation method, with a porous spherical morphology. On the basis of the fact that HA plays important roles in bone regeneration and promotes the differentiation, vascularization, and migration of stem cells, HA-cystamine (CYS) hydrogels with cleavable disulfide linkages were prepared to supply HA continuously for effective bone regeneration by their controlled degradation in vivo. Among seven different samples using Bio-OSS®, MGSB, and/or several kinds of HA hydrogels, MGSB/HA-CYS hydrogels resulted in the most significant bone regeneration in the calvarial critical bone defect of New Zealand white rabbits. Histological and histomorphometric analyses revealed that the bone regeneration by MGSB/HA-CYS hydrogels was as high as 43%, occupying 71% of the bone defect area with MGSB in the form of a calvarial bone plate in 4 weeks. After that, MGSB was bioabsorbed and replaced gradually with regenerated bones as observed in 8 weeks. Synchrotron X-ray imaging clearly confirmed the effective bone regeneration by MGSB/HA-CYS hydrogels, showing three-dimensional micron-scale morphologies of regenerated bones interconnected with MGSB. In addition, sequential nondestructive synchrotron X-ray tomographic analysis results from anterior to posterior of the samples were well matched with the histomorphometric analysis results. The clinically feasible artificial bone substitutes of MGSB/HA-CYS hydrogels will be investigated further for various bone tissue engineering applications using the synchrotron X-ray bioimaging systems.

Surface modification with fibrin/hyaluronic acid hydrogel on solid-free form-based scaffolds followed by BMP-2 loading to enhance bone regeneration

Bone tissue engineering often requires a well-defined scaffold that is highly porous. The multi-head deposition system (MHDS), a form of solid freeform fabrication, has raised great interest as a method for fabricating scaffolds, since it yields a highly porous inter-connective structure without the use of cytotoxic solvents, and permits the diffusion of nutrients and oxygen. However, this method is not suitable for introducing proteins, as it includes a heating process. Hydrogels incorporated with protein coating of the scaffold surface could overcome this MHDS limitation. In the present study, the surface of a scaffold fabricated using MHDS was coated with a mixture of fibrin and hyaluronic acid (HA) and used as a vehicle for delivery of both bone morphogenetic protein-2 (BMP-2) and adipose-derived stromal cells (ASCs). Fibrin/HA coating of the scaffold significantly enhanced initial cell attachment. Furthermore, the in vitro release of BMP-2 from fibrin/HA-coated scaffolds was sustained for 3 days and it stimulated the alkaline phosphatase activity of ASCs seeded on the scaffold for 10 days more actively and continuously than did the soluble BMP-2 that was added to the culture media, not the scaffold itself. Importantly, the transplantation of undifferentiated ASCs inoculated on BMP-2-loaded, fibrin/HA-coated scaffolds resulted in more improved bone formation and mineralization than did the transplantation of undifferentiated ASCs seeded on uncoated scaffolds or on fibrin/HA-coated scaffolds without BMP-2, but containing BMP-2 in the cell suspension medium. These results show that BMP-2-loaded, fibrin/HA-coated scaffolds fabricated using MHDS may be useful in stimulating bone regeneration from undifferentiated ASCs in vivo.

Spin-orbit qubits of rare-earth-metal ions in axially symmetric crystal fields

Contrary to the well-known spin qubits, rare-earth-metal qubits are characterized by a strong influence of crystal field due to large spin-orbit coupling. At low temperature and in the presence of resonance microwaves, it is the magnetic moment of the crystal-field ground state which nutates (for several micros) and the Rabi frequency Omega(R) is anisotropic. Here, we present a study of the variations of Omega(R)(H(0)) with the magnitude and direction of the static magnetic field H(0) for the odd 167Er isotope in a single crystal CaWO(4):Er(3+). The hyperfine interactions split the Omega(R)(H(0)) curve into eight different curves which are fitted numerically and described analytically. These "spin-orbit qubits" should allow detailed studies of decoherence mechanisms which become relevant at high temperature and open new ways for qubit addressing using properly oriented magnetic fields.

Double contrast-enhanced MRI of viral hepatitis-induced cirrhosis: correlation of gross morphological signs with hepatic fibrosis

The purpose of this study was to evaluate the diagnostic ability of the expanded gallbladder fossa and right posterior hepatic notch signs for hepatic fibrosis determined by double contrast-enhanced MRI. For patients with chronic viral hepatitis B (n = 96) or hepatitis C (n = 13) who underwent gadopentate dimeglumine-enhanced dynamic MRI followed by ferucarbotran-enhanced gradient-echo imaging, the degree of parenchymal fibrosis was categorised into three groups based on the extent of reticulation and nodularity: (1) pre-cirrhotic or minimal fibrosis; (2) mild to moderate fibrosis; (3) advanced cirrhosis. Each group was evaluated for the presence of a sharp notch in the posterior-medial surface of the right lobe of the liver and expanded gallbladder fossa. The expanded gallbladder fossa sign gradually increased with an increasing degree of fibrosis (Group 1, 50%; Group 2, 61%; Group 3, 78%), and there was no significant difference (p>0.5) between hepatitis B (67%) and C (73%). In the case of the right posterior hepatic notch sign, only 6% of Group 1 and Group 2 patients were positive; 27% of hepatitis B patients and 90% of hepatitis C patients in Group 3 exhibited the sign (p<0.05). Owing to its low prevalence, even in advanced cirrhosis, the right posterior hepatic notch sign is of little value in the diagnosis of cirrhosis due to chronic hepatitis B virus infection, whereas an expanded gallbladder fossa could be used as a non-specific indicator of early fibrosis before the gross appearance of advanced hepatic fibrosis.

Physicochemical properties, and antioxidant and antimicrobial effects of garlic and onion powder in fresh pork belly and loin during refrigerated storage

Pork loin and belly cuts were pumped to 110% of their original weight with solutions containing 5% of various ingredients (sodium ascorbate, garlic, and onion powder), and evaluated the physicochemical properties, and antioxidant and antimicrobial activities during refrigerated storage at 8 degrees C. The addition of garlic and onion powder tended to increase redness (a) and yellowness (b) in both the belly lean and loin with the exception of a few cases. Free fatty acid values in both pork belly and loin cuts were reduced with the addition of these ingredients, as compared to the control. Significant differences in peroxide values were observed in sodium ascorbate and garlic-injected belly, and in sodium ascorbate and onion-injected loin, as compared to the control. Thiobarbituric acid reactive substance values in the pork belly with garlic or onion powder were significantly lower than in the belly without these ingredients or with sodium ascorbate (P < 0.05). Total plate counts were lower in both the belly and loin containing garlic and onion powder, as compared to the control. In both the belly and loin cuts, the content of oxidative products (volatile compounds) was reduced with the addition of garlic and onion powder, particularly the aldehydes (hexanal). Overall, garlic and onion in enhanced meats showed an antioxidant activity as effective as that of sodium ascorbate and also an antimicrobial effect to inhibit the growth of total bacteria and Enterobacteriaceae.

[cDNA cloning and analysis of tissue-specific gene expression of rat urocortin II]

The corticotropin-releasing hormone (CRH) family of neuropeptides includes CRH (a 41 amino acid hypothalamic peptide) and urocortin. Corticotropin-releasing factor (CRF), a peptide first isolated from mammalian, plays an important role in the regulation of the pituitary-adrenal axis, and in endocrine, autonomic, immune and behavioral responses to stress. In this study we cloned rat urocortin II (UCNII) cDNA from rat mid-brain by RT-PCR. The rat UCNII clone contained an open reading frame (ORF) coding 109 amino acids which shared 90% and 63% homology with mouse and human homologues, respectively, The expression of UCN HII mRNA is mainly distributed in bone marrow, ovary, uterus, hypophysis, adrenal gland, and skin. In this study, rat recombinant UCN was expressed in E. coli and purified in active form. Furthermore, purified recombinant UCN II protein specifically binds to CRF receptor 2 in rat ROS 17/2.8 and GH3 cells by flow-cytometry analysis. UCN II cDNA clone obtained in this study will be useful for further investigation on behavioral responses to stress in rats.

Caspase-3 activation as a key factor for HBx-transformed cell death

OBJECTIVES

Nuclear factor-kappa B (NF-kappaB) activation has been associated with the tumorigenic growth of hepatitis B virus X protein (HBx)-transformed cells. This study was aimed to find a key target for treatment of HBx-mediated cancers.

MATERIALS AND METHODS

NF-kappaB activation, endoplasmic reticulum-stress (ER-stress), caspase-3 activation, and cell proliferation were evaluated after Chang/HBx cells permanently expressing HBx viral protein were treated with inhibitors of NF-kappaB, proteasome and DNA topoisomerase.

RESULTS

Inhibition of NF-kappaB transcriptional activity by transient transfection with mutant plasmids encoding Akt1 and glycogen synthase kinase-3beta (GSK-3beta), or by treatment with chemical inhibitors, wortmannin and LY294002, showed little effect on the survival of Chang/HBx cells. Furthermore, IkappaBalpha (S32/36A) mutant plasmid or other NF-kappaB inhibitors, 1-pyrrolidinecarbonidithioic acid and sulphasalazine, were also shown to have little effect on the cell proliferation. By contrast, proteasome inhibitor-1 (Pro1) and MG132 enhanced the HBx-induced ER-stress response and the subsequent activation of caspase-12, -9 and -3 and reduced cell proliferation. Camptothecin (CPT), however, triggered activation of caspase-3 without induction of caspase-12, and reduced cell proliferation. In addition, CPT-induced cell death was reversed by pre-treatment with z-DEVD, a caspase-3-specific inhibitor.

CONCLUSIONS

Detailed exploitation of the regulators of caspase-3 activation could open the gate for finding an efficient target for development of anticancer therapeutics against HBx-transformed hepatocellular carcinoma.

Dissipation behavior of lufenuron, benzoylphenylurea insecticide, in/on Chinese cabbage applied by foliar spraying under greenhouse conditions

Chinese cabbage has long been consumed as a staple food by the Koreans in various forms of fresh, salted, or fermented as kimchi. To fulfill the off-season demand for this crop, it has become a common practice to be cultivated under greenhouse conditions. Since pesticide residues in/on leafy vegetables have strongly concerned with food safety in the Korean society, the changes of lufenuron residues, in/on Chinese cabbage applied by foliar spraying under greenhouse conditions was investigated. Lufenuron 5% emulsifiable concentrate (EC) was sprayed with diluted solution of recommended and double doses to the crop. The shoots of the cabbage were harvested immediately after spraying, and sequentially the harvests were conveyed to analyze the residual amounts. The deposited level of the analyte in/on Chinese cabbage under greenhouse conditions seemed to be difficult to produce the crop with 0.2 ppm of maximum residue limit (MRL) of the Korea Food and Drug Administration (KFDA).

Screening of magnetic moments in PuAm alloy: local density approximation and dynamical mean field theory study

The puzzling absence of Pu magnetic moments in a PuAm environment is explored using the self-consistent dynamical mean field theory calculations in combination with the local density approximation. We argue that delta-Pu-Am alloys provide an ideal testbed for investigating the screening of moments from the single impurity limit to the dense limit. Several important effects can be studied: volume expansion, shift of the bare Pu on-site f energy level, and the reduction of the hybridization cloud resulting from the collective character of the Kondo effect in the Anderson lattice. These effects compensate each other and result in a coherence scale, which is independent of alloy composition, and is around 800 K.

[Cloning of rat TARC cDNA and analysis of tissue-specific mRNA expression]

Thymus and activation-regulated chemokine (TARC) is one that selectively controls the migration of type 2-helper T lymphocytes into inflammatory lesions. TARC is a CC chemokine, and plays an essential role in recruiting CC chemokine receptor 4-positive Th2 cells to allergic lesions. We cloned TARC cDNA from rat thymus using RT-PCR. The rat TARC clone contained a full-length open reading frame encoding 93 amino acids that showed 83% and 66% homology with mouse and human homologs, respectively. The expression of TARC mRNA was mainly in the lymphoid organs, for example, the thymus, spleen, and lymph node. The recombinant TARC was expressed in Escherichia coli and purified in an active form. In addition, the purified rat TARC with S-tagged specifically binds to human CCR4 in CD4.CCR4-transfected HOS cells by Cell-binding assay using flow-cytometry. The TARC cDNA clones obtained in this study will be valuable for future studies on allergic diseases in rats.

Large spin diffusion length in an amorphous organic semiconductor

We directly measured a spin diffusion length (lambdas) of 13.3 nm in amorphous organic semiconductor (OS) rubrene (C42H28) by spin polarized tunneling. In comparison, no spin-conserved transport has been reported in amorphous Si or Ge. Absence of dangling bond defects can explain the spin transport behavior in amorphous OS. Furthermore, when rubrene barriers were grown on a seed layer, the elastic tunneling characteristics were greatly enhanced. Based on our findings, lambdas in single-crystalline rubrene can be expected to reach even millimeters, showing the potential for organic spintronics development.

Correlated electronic structure of LaO1-xFxFeAs

We compute the electronic structure, momentum resolved spectral function and optical conductivity of the new superconductor LaO1-xFxFeAs within the combination of the density functional theory and dynamical mean field theory. We find that the compound in the normal state is a strongly correlated metal and the parent compound is a bad metal at the verge of the metal insulator transition. We argue that the superconductivity is not phonon mediated.

Modeling the localized-to-itinerant electronic transition in the heavy fermion system CeIrIn5

We address the fundamental question of crossover from the localized to the itinerant state of a paradigmatic heavy fermion material: CeIrIn5. The temperature evolution of the one-electron spectra and the optical conductivity are predicted from first-principles calculation. The buildup of coherence in the form of a dispersive many-body feature is followed in detail, and its effects on the conduction electrons of the material are revealed. We find multiple hybridization gaps and link them to the crystal structure of the material. Our theoretical approach explains the multiple peak structures observed in optical experiments and the sensitivity of CeIrIn5 to substitutions of the transition metal element and may provide a microscopic basis for the more phenomenological descriptions currently used to interpret experiments in heavy fermion systems.

Optimized conditions for the extraction of secondary volatile metabolites in Angelica roots by accelerated solvent extraction

Accelerated solvent extraction (ASE) of three common Angelica species found in Asia: Angelica sinensis (Oliv.) Diels from China, Angelica acutiloba (Sieb. et Zucc.) Kitagawa from Japan, and Angelica gigas Nakai from Korea was investigated. Preliminary experiments, including the selection of the solvent, extraction time, pressure, static cycle and time were investigated to optimize experimental parameters. Kováts indices and mass spectra were used to identify the components in the various fractions. These were then confirmed using gas chromatography-mass spectrometry (GC-MS). A total of 18 compounds were identified, with qualitative differences and similarities observed among the cultivars. From the 18 compounds found in the ASE extract of danggui cultivars, the major components were decursin, decursinol angelate (A. gigas); butylidene dihydrophthalide, 4-hydroxy-4-methyl-2-pentanone (A. sinensis); and 9,12-octadecanoic acid in Angelica acutiloba. The optimum ASE operating conditions were n-hexane as extraction solvent, extraction temperature and pressure of 80 degrees C and 1500 atm, respectively, static cycle of 2 min, and static time of 10 min. Under these conditions, the percentages of main analytes were increased.

Directed differentiation of human embryonic stem cells towards a pancreatic cell fate

AIMS/HYPOTHESIS

The relative lack of successful pancreatic differentiation of human embryonic stem cells (hESCs) may suggest that directed differentiation of hESCs into definitive endoderm and subsequent commitment towards a pancreatic fate are not readily achieved. The aim of this study was to investigate whether sequential exposure of hESCs to epigenetic signals that mimic in vivo pancreatic development can efficiently generate pancreatic endodermal cells, and whether these cells can be further matured and reverse hyperglycaemia upon transplantation.

MATERIALS AND METHODS

The hESCs were sequentially treated with serum, activin and retinoic acid (RA) during embryoid body formation. The patterns of gene expression and protein production associated with embryonic germ layers and pancreatic endoderm were analysed by RT-PCR and immunostaining. The developmental competence and function of hESC-derived PDX1-positive cells were evaluated after in vivo transplantation.

RESULTS

Sequential treatment with serum, activin and RA highly upregulated the expression of the genes encoding forkhead box protein A2 (FOXA2), SRY-box containing gene 17 (SOX17), pancreatic and duodenal homeobox 1 (PDX1) and homeobox HB9 (HLXB9). The population of pancreatic endodermal cells that produced PDX1 was significantly increased at the expense of ectodermal differentiation, and a subset of the PDX1-positive cells also produced FOXA2, caudal-type homeobox transcription factor 2 (CDX2), and nestin (NES). After transplantation, the PDX1-positive cells further differentiated into mature cell types producing insulin and glucagon, resulting in amelioration of hyperglycaemia and weight loss in streptozotocin-treated diabetic mice.

CONCLUSIONS/INTERPRETATION

Our strategy allows the progressive differentiation of hESCs into pancreatic endoderm capable of generating mature pancreatic cell types that function in vivo. These findings may establish the basis of further investigations for the purification of transplantable islet progenitors derived from hESCs.

Fluctuating valence in a correlated solid and the anomalous properties of δ-plutonium

Although the nuclear properties of the late actinides (plutonium, americium and curium) are fully understood and widely applied to energy generation, their solid-state properties do not fit within standard models and are the subject of active research. Plutonium displays phases with enormous volume differences, and both its Pauli-like magnetic susceptibility and resistivity are an order of magnitude larger than those of simple metals. Curium is also highly resistive, but its susceptibility is Curie-like at high temperatures and orders antiferromagnetically at low temperatures. The anomalous properties of the late actinides stem from the competition between itinerancy and localization of their f-shell electrons, which makes these elements strongly correlated materials. A central problem in this field is to understand the mechanism by which these conflicting tendencies are resolved in such materials. Here we identify the electronic mechanisms responsible for the anomalous behaviour of late actinides, revisiting the concept of valence using a theoretical approach that treats magnetism, Kondo screening, atomic multiplet effects and crystal field splitting on the same footing. We find that the ground state in plutonium is a quantum superposition of two distinct atomic valences, whereas curium settles into a magnetically ordered single valence state at low temperatures. The f(7) configuration of curium is contrasted with the multiple valences of the plutonium ground state, which we characterize by a valence histogram. The balance between the Kondo screening and magnetism is controlled by the competition between spin-orbit coupling, the strength of atomic multiplets and the degree of itinerancy. Our approach highlights the electronic origin of the bonding anomalies in plutonium, and can be applied to predict generalized valences and the presence or absence of magnetism in other compounds starting from first principles.

Acute-phase response alters the disposition kinetics of cefepime following intravenous administration to rabbits

The effect of experimentally induced fever on the pharmacokinetics of cefepime administered intravenously at a dose of 75 mg/kg bw was studied in six healthy rabbits. The study was conducted in two consecutive phases, separated by a washout period of 2 weeks. Infection was induced by the intravenous inoculation of 5 x 10(8) cfu of Escherichia coli 24 h before the pharmacokinetic investigation was carried out. Serial blood samples for cefepime concentration determination were obtained for 48 h following drug administration. The concentrations of cefepime in the plasma were determined by a quantitative microbiological assay using an agar-gel diffusion method employing Bacillus subtilis ATCC 6633 as the test organism, with a level of detectability of approximately 0.10 microg/ml. Cefepime plasma concentrations versus time were evaluated by non-compartmental methods using WinNonLin. Cefepime was well tolerated and no serious adverse events were observed. Rectal temperature increased 1 degree C 24 h post injection in infected animals. Highly significant differences in the blood plasma concentrations of cefepime were observed between febrile and healthy animals at all the sampling times. This could explain the greater area under the plasma level-time curve of the drug in febrile compared with healthy animals. The results from pharmacokinetic calculations showed that both the distribution volume at steady state (V (dss)) and body clearance (CL(tot)) were affected in febrile as compared to healthy animals. The mean values of V (dss) and CL(tot) of cefepime in healthy rabbits were 1.168 L/kg and 0.303 L/kg/h, respectively. As compared with healthy animals, the mean estimates of V (dss) (0.917 L/kg) and CL(tot) (0.205 L/kg per h) of cefepime were significantly lower, whereas t (1/2lambda), MRT and AUMC were significantly higher in febrile rabbits. It is concluded that, although experimental infection had an effect on the disposition kinetics of cefepime in healthy and febrile rabbits, this was not sufficiently pronounced to require alteration of the dosage during disease.

Characterization of the relationship between serum and milk residue disposition of ceftriaxone in lactating ewes

The present study was planned to investigate the serum disposition kinetics and the pattern of ceftriaxone elimination in milk and urine of lactating ewes (n = 6) following i.v. and i.m. administration. A crossover study was carried out in two phases separated by 15 days. Ceftriaxone was administered at a dosage of 10 mg/kg b.w. in all animals. Serum, milk and urine samples were collected between 0 and 72 h and a modified agar diffusion bioassay method was used to determine the percentage of protein binding and to measure serum, urine and milk concentrations of ceftriaxone. The drug was detected between 5 min and 48 h postdosing. Concentrations of 0.56 (10 h) and 0.52 (12 h), 0.22 (10 h) and 0.19 (12 h), and 2.18 (24 h) and 2.11 (48 h) mug/mL were measured in serum, milk and urine following i.v. and i.m. administration, respectively. Individual pharmacokinetic parameters were determined by fitting a two-compartment model to the serum and one-compartment open model to the milk concentration-time profiles. After i.v. dosing, the elimination rate constant and elimination half-life were 0.4 +/- 0.05/h and 1.75 +/- 0.02 h, respectively. The volume of distribution at steady state (V(dss)) of 0.28 +/- 0.15 L/kg reflected limited extracellular distribution of the drug with total body clearance (Cl(tot)) of 0.14 +/- 0.10 L/h/kg. Following i.m. administration, the mean T(max obs), C(max obs), t(1/2el) and AUC values for serum data were: 0.75 h, 23.16 +/- 2.94 microg/mL, 1.77 +/- 0.24 h and 67.55 +/- 6.51 microgxh/mL, respectively. For milk the data were: 1.0 h, 8.15 +/- 0.71 mug/mL, 2.2 +/- 0.34 h and 26.6 +/- 5.14 microgxh/mL, respectively. The i.m. bioavailability was 83.6% and the binding percentage of ceftriaxone to serum protein was 33%. Concentrations of ceftriaxone in milk produced by clinically normal mammary glands of ewes were consistently lower than in serum; the kinetic value AUC(milk)/AUC(serum) and C(max milk)/C(max serum) ratios was<0.4. These low values indicated poor distribution and penetration of ceftriaxone from the bloodstream to the mammary gland of lactating ewes following both routes.

Determination of volatile flavor components in danggui cultivars by solvent free injection and hydrodistillation followed by gas chromatographic–mass spectrometric analysis

The rhizome of Angelica gigas Nakai, Angelica sinensis Diels and Angelica acutiloba Kitagawa (Umbelliferae) were chopped and extracted by hydrodistillation (HD) and solvent free solid injector (SFSI) methods to obtain the volatile compounds that were then characterized and identified by gas chromatography-mass spectrometry (GC/MS). SFSI extraction yielded a generally higher amount of volatile compounds than that produced by HD. A total of 48 components [including terpenes (8), aldehydes (4), alcohol (2), coumarins (9), Phthalide (3), acids (2) and sterols (2)] were identified by SFSI and gas chromatography-mass spectrometry from the three species of danggui cultivars, whereas, 24-essential oil was obtained by HD for Korean danggui only. According to these analyses, several coumarin derivatives such as decursinol angelate (16.83%) and decursin (29.34%) were found to be the dominant ones, followed by lomatin (10.25%) and marmesin (9.33%) in Korean danggui. Furfural and butylidene phthalide were the main components in Japanese in addition to butylidene dihydro-phthalide in Chinese danggui. Some parameters affecting the extraction efficiency such as injector temperature, injection time and pre-heating time were optimized. The results showed that the SFSI-method gave a higher yield of components with higher molecular mass than hydrodistillation. SFSI required little time to prepare the sample, little sample mass and a small quantity of organic solvent was needed. It can be concluded that analysis of volatile flavor compounds by SFSI in combination with gas chromatography/mass spectrometry is a suitable monitoring technique to differentiate danggui cultivars.

Electronic structures of RTe2 (R = La,Ce): a clue to the pressure-induced superconductivity in CeTe1.82

Electronic structures of RTe2 (R=La,Ce) have been investigated by using the local spin density approximation (LSDA) and the LSDA + U (U: on-site Coulomb interaction) band methods. Both LaTe2 and CeTe2 show the very similar Fermi surface nesting features along the [100] direction, which drive the charge-density wave (CDW) instability in the Te(1) sheets. The contribution near E(F) from Ce 4f states is negligible in agreement with the measured ARPES spectra. In the semimetallic CDW-distorted RTe2, both Te vacancy and pressure induce the charge transfer from Te(1) 5p to R 5d states, producing the enhanced density of states at E(F). We suggest that these increased self-doped Te(1) 5p hole carriers are responsible for the pressure-induced superconductivity in nonstoichiometric CeTe1.82.

Lower trunk muscle activity during the tennis serve

Prior electromyographic (EMG) analyses of the tennis serve have focused on the muscles in the hitting arm and shoulder region. This preliminary study aimed to examine the muscle activation patterns of selected lower trunk muscles during three different types of tennis serve--flat, topspin, and slice. Five male highly skilled tennis players completed 10 trials for each type of serve. Surface EMG electrodes were used to monitor the rectus abdominis (RA), external oblique (EO), internal oblique (IO), and lumbar erector spinae (ES) muscles. For each subject, the two trials with the highest self-reported ratings were analysed. Average EMG levels during each phase of a tennis serve for each muscle were analysed using a non-parametric ANOVA design. No major differences in muscle activation pattern were found across different serve types, and bilateral differences in muscle activation were more pronounced in RA and EO than in IO and ES muscles. The abdominal muscles were more active in the topspin than in the other two types of serves during the upward swing of the racket. An appreciable amount of abdominal/low back and bilateral co-activation was observed during certain phases of the serve. The co-activation of lower trunk muscles may help to stabilise the lumbar spine during the arch back and forward swing phases of the serve. The results reinforce the importance of abdominal and low back exercises in the strength and rehabilitation programs designed for tennis players.

Use of the Keele injector for sample introduction for gas chromatographic analysis of vinclozolin in lettuces

We examined a Keele injector for sample introduction for gas chromatographic analysis of vinclozolin treated in lettuces. Samples in milligram quantity were introduced into a glass tube in a Keele injector at a gas chromatograph injection port. The glass tube was then crushed to allow the sample to carry onto a capillary column in a normal manner. The standard calibration curve for quantitative detection of vinclozolin was obtained by determining vinclozolin spiked in samples at variable concentrations. The calibration curve showed a linear response to vinclozolin ranging from 0.05 to 1.0 microg/g, giving a slope value of 174.8, the y-intercept value of -2.8146 and the mean r2-value of 0.9994. Limit of quantification for vinclozolin was 0.05 microg/g by this method, comparable to 0.01 microg/g by a normal injector. When samples treated previously with vinclozolin were determined by the Keele injector, vinclozolin was found to be about 30% lower as compared to a normal method, suggesting about 70% recovery of the spiked vinclozolin by the Keele injector. From these results, the Keele injector was suggested to be potential for sample introduction in gas chromatographic analysis of vinclozolin in lettuce samples.

Matrix formalism of electromagnetic wave propagation through multiple layers in the near-field region: application to the flat panel display

We have developed an electromagnetic (EM) wave propagation theory through a single layer and multiple layers in the near-field and far-field regions, and have constructed a matrix formalism in terms of the boundary conditions of the EM waves. From the shielding efficiency (SE) against EM radiation in the near-field region calculated by using the matrix formalism, we propose that the effect of multiple layers yields enhanced shielding capability compared to a single layer with the same total thickness in conducting layers as the multiple layers. We compare the intensities of an EM wave propagating through glass coated with conducting indium tin oxide (ITO) on one side and on both sides, applying it to the electromagnetic interference (EMI) shielding filter in a flat panel display such as a plasma display panel (PDP). From the measured intensities of EMI noise generated by a PDP loaded with ITO coated glass samples, the two-side coated glass shows a lower intensity of EMI noise compared to the one-side coated glass. The result confirms the enhancement of the SE due to the effect of multiple layers, as expected in the matrix formalism of EM wave propagation in the near-field region. In the far-field region, the two-side coated glass with ITO in multiple layers has a higher SE than the one-side coated glass with ITO, when the total thickness of ITO in both cases is the same.

Both E6 and E7 oncoproteins of human papillomavirus 16 inhibit IL-18-induced IFN-gamma production in human peripheral blood mononuclear and NK cells

Cervical carcinoma is the predominant cancer among malignancies in women throughout the world, and human papillomavirus (HPV) 16 is the most common agent linked to human cervical carcinoma. The present study was performed to investigate the mechanisms of immune escape in HPV-induced cervical cancer cells. The presence of HPV oncoproteins E6 and E7 in the extracellular fluids of HPV-containing cervical cancer cell lines SiHa and CaSki was demonstrated by ELISA. The effect of HPV 16 oncoproteins E6 and E7 on the production of IFN-gamma by IL-18 was assessed. E6 and E7 proteins reduced IL-18-induced IFN-gamma production in both primary PBMCs and the NK0 cell line. FACS analysis revealed that the viral oncoproteins reduced the binding of IL-18 to its cellular surface receptors on NK0 cells, whereas there was no effect of oncoproteins on IL-1 binding to its surface IL-1 receptors on D10S, a subclone of the murine Th cell D10.G4.1. In vitro pull-down assays also revealed that the viral oncoproteins and IL-18 bound to IL-18R alpha-chain competitively. These results suggest that the extracellular HPV 16 E6 and E7 proteins may inhibit IL-18-induced IFN-gamma production locally in HPV lesions through inhibition of IL-18 binding to its alpha-chain receptor. Down-modulation of IL-18-induced immune responses by HPV oncoproteins may contribute to viral pathogenesis or carcinogenesis.

Evaluation of the catalytic mechanism of AICAR transformylase by pH-dependent kinetics, mutagenesis, and quantum chemical calculations

The catalytic mechanism of 5-aminoimidazole-4-carboxamide ribonucleotide transformylase (AICAR Tfase) is evaluated with pH dependent kinetics, site-directed mutagenesis, and quantum chemical calculations. The chemistry step, represented by the burst rates, was not pH-dependent, which is consistent with our proposed mechanism that the 4-carboxamide of AICAR assists proton shuttling. Quantum chemical calculations on a model system of 5-amino-4-carboxamide imidazole (AICA) and formamide using the B3LYP/6-31G level of theory confirmed that the 4-carboxamide participated in the proton-shuttling mechanism. The result also indicated that the amide-assisted mechanism is concerted such that the proton transfers from the 5-amino group to the formamide are simultaneous with nucleophilic attack by the 5-amino group. Because the process does not lead to a kinetically stable intermediate, the intramolecular proton transfer from the 5-amino group through the 4-carboxamide to the formamide proceeds in the same transition state. Interestingly, the calculations predicted that protonation of the N3 of the imidazole of AICA would reduce the energy barrier significantly. However, the pK(a) of the imidazole of AICAR was determined to be 3.23 +/- 0.01 by NMR titration, and AICAR is likely to bind to the enzyme with its imidazole in the free base form. An alternative pathway was suggested by modeling Lys266 to have a hydrogen-bonding interaction with the N3 of the imidazole of AICAR. Lys266 has been implicated in catalysis based on mutagenesis studies and the recent X-ray structure of AICAR Tfase. The quantum chemical calculations on a model system that contains AICA complexed with CH3NH3+ as a mimic of the Lys residue confirmed that such an interaction lowered the activation energy of the reaction and likewise implicated the 4-carboxamide. To experimentally verify this hypothesis, we prepared the K266R mutant and found that its kcat is reduced by 150-fold from that of the wild type without changes in substrate and cofactor Km values. The kcat-pH profile indicated virtually no pH-dependence in the pH range 6-10.5. The results suggest that the ammonium moiety of Lys or Arg is important in catalysis, most likely acting as a general acid catalyst with a pK(a) value greater than 10.5. The H267A mutant was also prepared since His267 has been found in the active site and implicated in catalysis. The mutant enzyme showed no detectable activity while retaining its binding affinity for substrate, indicating that it plays a critical role in catalysis. We propose that His267 interacts with Lys266 to aid in the precise positioning of the general acid catalyst to the N3 of the imidazole of AICAR.

The Unexpected Catalytic Properties of a Heterodimer of GAR Transformylase

We have developed an efficient expression and purification protocol for a heterodimer of glycinamide ribonucleotide transformylase that was identified in incremental truncation libraries, a general combinatorial method for protein fragment complementation (M. Ostermeier, A. E. Nixon, J. H. Shim, and S. J. Benkovic, [1999], Proc. Natl. Acad. Sci. USA 96, 3562-3567). This heterodimer (B13) containing both a bisection point and a deletion in conserved residues close to the active site was expressed and purified in high yield using Intein methodology. The N-terminus fragment (1-111) and C-terminus fragment (M114-212) were also expressed separately as stable proteins. When these two fragments were mixed together, they associate at a highly specific 1:1 ratio to give only the active heterodimer, B13. The activity of B13 is comparable to that of the wild type and the pH-dependent kinetics of B13 turned out to be nearly identical to those of the wild type, indicating that B13 operates in the same mechanism as the wild type. This result demonstrated that cutting within conserved regions is a viable domain separation and confirmed the generality of using incremental truncation for protein fragment complementation.

Human AICAR transformylase: role of the 4-carboxamide of AICAR in binding and catalysis

We have prepared 4-substituted analogues of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) to investigate the specificity and mechanism of AICAR transformylase (AICAR Tfase). Of the nine analogues of AICAR studied, only one analogue, 5-aminoimidazole-4-thiocarboxamide ribonucleotide, was a substrate, and it was converted to 6-mercaptopurine ribonucleotide. The other analogues either did not bind or were competitive inhibitors, the most potent being 5-amino-4-nitroimidazole ribonucleotide with a K(i) of 0.7 +/- 0.5 microM. The results show that the 4-carboxamide of AICAR is essential for catalysis, and it is proposed to assist in mediating proton transfer, catalyzing the reaction by trapping of the addition compound. AICAR analogues where the nitrogen of the 4-carboxamide was derivatized with a methyl or an allylic group did not bind AICAR Tfase, as determined by pre-steady-state burst kinetics; however, these compounds were potent inhibitors of IMP cyclohydrolase (IMP CHase), a second activity of the bifunctional mammalian enzyme (K(i) = 0.05 +/- 0.02 microM for 4-N-allyl-AlCAR). It is proposed that the conformation of the carboxamide moiety required for binding to AICAR Tfase is different than the conformation required for binding to IMP CHase, which is supported by inhibition studies of purine ribonucleotides. It is shown that 5-formyl-AICAR (FAICAR) is a product inhibitor of AICAR Tfase with K(i) of 0.4 +/- 0.1 microM. We have determined the equilibrium constant of the transformylase reaction to be 0.024 +/- 0.001, showing that the reaction strongly favors AICAR and the 10-formyl-folate cofactor. The coupling of the AICAR Tfase and IMP CHase activities on a single polypeptide allows the overall conversion of AICAR to IMP to be favorable by coupling the unfavorable formation of FAICAR with the highly favorable cyclization reaction. The current kinetic studies have also indicated that the release of FAICAR is the rate-limiting step, under steady-state conditions, in the bifunctional enzyme and channeling is not observed between AICAR Tfase and IMP CHase.

Significance of serum and tissue carcinoembryonic antigen for the prognosis of gastric carcinoma patients

BACKGROUND AND OBJECTIVES

Carcinoembryonic antigen (CEA) has been widely accepted as a tumor marker useful in the diagnosis and management of colorectal carcinoma. When CEA levels are positive in patients with gastric carcinoma, they could be useful prognostic indicators. The value of CEA as a tumor marker for gastric carcinoma, however, remains a matter of controversy. The purpose of this study was to determine whether preoperative serum CEA value and tissue CEA staining are useful prognostic indicators for gastric carcinoma.

METHODS

We measured preoperative serum CEA levels by radioimmunoassay and stained tissue CEA production by tumor cells from gastric carcinomas using immunohistochemical staining in patients with gastric carcinoma.

RESULTS

The patients with preoperative serum CEA levels >10.0 ng/mL had a more prominent serosal invasion, much more lymph node involvement, more advanced stage and more poorly differentiated than did the patients with preoperative serum CEA levels <5.0 ng/mL. The survival rate of patients with serum CEA levels >10.0 ng/mL was poorer than those of patients with serum CEA levels between 5.0 and 10.0 ng/mL, and those of patients with serum CEA levels <5.0 ng/mL (P < 0.05). The preoperative serum CEA levels and tumor CEA-positivity were correlated (P < 0.05). In patients with lymph node metastases, the CEA-positivity (78.0%) was higher than in patients without lymph node metastasis (63.2%) (P < 0.05). A correlation was also found between the depth of tumor invasion and tissue CEA-positivity (P < 0.001). The postoperative survival rate was significantly better in the CEA-negative staining group (78.0%) than in the CEA-positive staining group (60.0%).

CONCLUSIONS

These data suggest that preoperative serum CEA levels and staining for CEA in gastric carcinoma tissue sections may have a predictive value in determining prognostic information for patients with resectable gastric carcinoma.

Design, synthesis, and biological evaluation of fluoronitrophenyl substituted folate analogues as potential inhibitors of GAR transformylase and AICAR transformylase

The examination results of a novel series of potential inhibitors of glycinamide ribonucleotide transformylase (GAR Tfase) and aminoimidazole carboxamide transformylase (AICAR Tfase) are reported. These agents incorporate an electrophilic fluoronitrophenyl group that can potentially react with an active site nucleophile or the substrate GAR/AICAR amine via nucleophilic aromatic substitution.

Significance of serum and tissue carcinoembryonic antigen for the prognosis of gastric carcinoma patients

BACKGROUND AND OBJECTIVES

Carcinoembryonic antigen (CEA) has been widely accepted as a tumor marker useful in the diagnosis and management of colorectal carcinoma. When CEA levels are positive in patients with gastric carcinoma, they could be useful prognostic indicators. The value of CEA as a tumor marker for gastric carcinoma, however, remains a matter of controversy. The purpose of this study was to determine whether preoperative serum CEA value and tissue CEA staining are useful prognostic indicators for gastric carcinoma.

METHODS

We measured preoperative serum CEA levels by radioimmunoassay and stained tissue CEA production by tumor cells from gastric carcinomas using immunohistochemical staining in patients with gastric carcinoma.

RESULTS

The patients with preoperative serum CEA levels >10.0 ng/mL had a more prominent serosal invasion, much more lymph node involvement, more advanced stage and more poorly differentiated than did the patients with preoperative serum CEA levels <5.0 ng/mL. The survival rate of patients with serum CEA levels >10.0 ng/mL was poorer than those of patients with serum CEA levels between 5.0 and 10.0 ng/mL, and those of patients with serum CEA levels <5.0 ng/mL (P < 0.05). The preoperative serum CEA levels and tumor CEA-positivity were correlated (P < 0.05). In patients with lymph node metastases, the CEA-positivity (78.0%) was higher than in patients without lymph node metastasis (63.2%) (P < 0.05). A correlation was also found between the depth of tumor invasion and tissue CEA-positivity (P < 0.001). The postoperative survival rate was significantly better in the CEA-negative staining group (78.0%) than in the CEA-positive staining group (60.0%).

CONCLUSIONS

These data suggest that preoperative serum CEA levels and staining for CEA in gastric carcinoma tissue sections may have a predictive value in determining prognostic information for patients with resectable gastric carcinoma.

Imposex in the rock shell, Thais clavigera, as evidence of organotin contamination in the marine environment of Korea

Imposex was measured in the rock shell, Thais clavigera, from the coast of the Korean peninsula. Frequency of imposex was 0% at two reference sites, but at 47 out of 61 sites, frequency of imposex was recorded as 100%. The degree of imposex was relatively high at the sites near a harbor and a shipyard. Tributyltin (TBT) and triphenyltin (TPT) concentrations in T. clavigera ranged from 5 to 508 ng/g and from 3 to 2460 ng/g, respectively. A significant positive relationship was found between degree of imposex and organotin concentration, whereas a significant negative relationship was obtained between female-to-male sex ratio and the degree of imposex. During a field transplantation of T. clavigera from a pristine area to a port, TBT and TPT were accumulated in T. clavigera, and imposex was induced. T. clavigera shows considerable potential as a bioindicator species of the adverse effects of TBT and TPT contamination.

Conformationally restricted analogues designed for selective inhibition of GAR Tfase versus thymidylate synthase or dihydrofolate reductase

The synthesis and evaluation of a series of conformationally restricted analogues of 10-formyl-tetrahydrofolate as potential inhibitors of glycinamide ribonucleotide transformylase (GAR Tfase) or aminoimidazole carboxamide transformylase (AICAR Tfase) are reported.

A combinatorial approach to hybrid enzymes independent of DNA homology

We present a methodology, termed incremental truncation for the creation of hybrid enzymes (ITCHY), that creates combinatorial fusion libraries between genes in a manner that is independent of DNA homology. We compared the ability of ITCHY and DNA shuffling to create interspecies fusion libraries between fragments of the Escherichia coli and human glycinamide ribonucleotide transformylase genes, which have only 50% identity on the DNA level. Sequencing of several randomly selected positives from each library illustrated that ITCHY identified a more diverse set of active fusion points including those in regions of nonhomology and those with crossover points that diverged from the sequence alignment. Furthermore, some of the hybrids found by ITCHY that were fused at nonhomologous locations had activities that were greater than or equal to the activity of the hybrids found by DNA shuffling.

Limited stress response in Streptococcus pneumoniae

In Streptococcus pneumoniae, heat shock induces the synthesis of 65-, 73-, and 84-kDa proteins, and ethanol shock induces a 104-kDa protein. In this study, the 65-, 84-, and 104-kDa proteins were identified as members of the GroEL, ClpL and alcohol dehydrogenase families, respectively, and the general properties of the stress response of S. pneumoniae to several other stresses were characterized. However, several stresses which are known to induce stress responses in Escherichia coli and Bacillus subtilis failed to induce any high molecular weight heat-shock proteins (HSPs) such as GroEL and DnaK homologues. A minor temperature shift from 30 to 37 C triggered induction of the homologues of DnaK and GroEL of E. coli. These features may provide a foundation for evaluating the role of heat-shock proteins relative to the physiology and pathogenesis of pneumococcus.