bluuebunny/crossref_metadata_2025 huggingface dataset:
Conserved Footprints of APOBEC3G on Hypermutated Human Immunodeficiency Virus Type 1 and Human Endogenous Retrovirus HERV-K(HML2) Sequences
Authors: Armitage Andrew E. , Katzourakis Aris , de Oliveira Tulio , Welch John J. , Belshaw Robert , Bishop Kate N. , Kramer Beatrice , McMichael Andrew J. , Rambaut Andrew , Iversen Astrid K. N.
Published: June 2008

The human polynucleotide cytidine deaminases APOBEC3G (hA3G) and APOBEC3F (hA3F) are antiviral restriction factors capable of inducing extensive plus-strand guanine-to-adenine (G-to-A) hypermutation in a variety of retroviruses and retroelements, including human immunodeficiency virus type 1 (HIV-1). They differ in target specificity, favoring plus-strand 5′GG and 5′GA dinucleotide motifs, respectively. To characterize their mutational preferences in detail, we analyzed single-copy, near-full-length HIV-1 proviruses which had been hypermutated in vitro by hA3G or hA3F. hA3-induced G-to-A mutation rates were significantly influenced by the wider sequence context of the target G. Moreover, hA3G, and to a lesser extent hA3F, displayed clear tetranucleotide preference hierarchies, irrespective of the genomic region examined and overall hypermutation rate. We similarly analyzed patient-derived hypermutated HIV-1 genomes using a new method for estimating reference sequences. The majority of these, regardless of subtype, carried signatures of hypermutation that strongly correlated with those induced in vitro by hA3G. Analysis of genome-wide hA3-induced mutational profiles confirmed that hypermutation levels were reduced downstream of the polypurine tracts. Additionally, while hA3G mutations were found throughout the genome, hA3F often intensely mutated shorter regions, the locations of which varied between proviruses. We extended our analysis to human endogenous retroviruses (HERVs) from the HERV-K(HML2) family, finding two elements that carried clear footprints of hA3G activity. This constitutes the most direct evidence to date for hA3G activity in the context of natural HERV infections, demonstrating the involvement of this restriction factor in defense against retroviral attacks over millions of years of human evolution.
Fungi occurring in the achenes of sunflower (Helianthus annuus)
Authors: Roberts R. G. , Robertson J. A. , Hanlin R. T.
Published: June 2008

More than 28 000 oil-type and confectionary sunflower seeds (achenes) from several production areas in the United States were surface sterilized and plated onto agar media, and the fungi that grew from them were identified. Ninety-eight species in 38 genera were identified from graded samples (grade No. 1, grade No. 2, and sample grade) of seed stored at 20 °C at 63, 83, and 93% relative humidities and from developing seed field-grown in Georgia. Sixty-four fungal taxa are reported from sunflower seed for the first time. The internal mycoflora of sunflower seed grown in Georgia differed in 2 consecutive years; pre-harvest invasion of developing seed by storage fungi occurred during the dry growing season of 1983, and species diversity was greater than in 1984, which had a relatively wet growing season. Although fewer total genera and species were isolated in 1984, the percent of seed infected by and the number of species of Fusarium present in seed produced during the wet year were much greater than during the dry year. Forty-five potentially mycotoxigenic and five thermophilic taxa were recorded. Five species of Microascus previously unknown from sunflower seed were isolated.
The stomatal complex of Persea borbonia
Authors: Edwards H. Herbert
Published: June 2008

The ultrastructure of the guard cell complex of Persea borbonia is described. The guard cells are embedded in the midregion of the ventral wall of subsidiary cells. The outer portions of the subsidiary cell wall is extensively thickened forming a domelike structure with a large slot opening projecting above the stomatal aperture. The outer walls of epidermal cells are also extensively thickened. The fused ventral cell walls have perforations resulting in cytoplasmic continuity between guard cells. The guard cells and subsidiary cells contain normal cytoplasmic constituents, including chloroplasts. Preliminary studies of three other Lauraceae species, Persea americana, Sassafras albidum, and Laurus nobilis, indicate a similarly structured stomatal complex.
Cluster root formation by Gymnostoma papuanum (Casuarinaceae) in relation to aeration and mineral nutrient availability in water culture
Authors: Racette Suzanne , Louis Isabelle , Torrey John G.
Published: June 2008

The term cluster root is used to refer to a dense cluster of determinate lateral roots (rootlets), in preference to the terms proteoid root and proteoid-like root used by other authors. Cluster roots are often formed by the actinorhizal plant Gymnostoma papuanum. In water culture, cluster root formation by G. papuanum was influenced by aeration, phosphorus level, and nitrogen source. Aeration was a critical factor, with nonaerated rooted cuttings having far fewer cluster roots than aerated ones. Phosphorus deficiency was the single nutrient deficiency that led to increased cluster root formation. Seedlings, grown under conditions of either low (0.8 mg∙L−1) or no phosphorus, responded by devoting a greater portion of root growth to the production of cluster roots, with no overall reduction in root growth for 6 weeks. The response to varying phosphorus level was modified by providing nitrogen in different forms. Supplying nitrogen as ammonium resulted in low levels of cluster root formation. Supplying nitrate to nodulated seedlings led to an increase in cluster root formation in comparison with plants that depended solely upon dinitrogen fixation by Frankia. Greatest cluster root formation occurred on plants grown in aerated water cultures supplied with nitrate and with little or no phosphorus. Key words: Gymnostoma papuanum, cluster roots, proteoid roots, phosphorus deficiency.
Unusual ascospore germination in Hypoxylon fragiforme: first seps in the establishment of an endophytic symbiosis
Authors: Chapela I. H. , Petrini O. , Petrini L. E.
Published: June 2008

An unusual germination mechanism in ascospores of Hypoxylon fragiforme is described and illustrated. In this xylariaceous, endophytic fungus, germination always involved the emergence of a bivalved, flexible structure from an outer rigid shell, formed by a differentiated transparent wall layer, and resulted in the exposure of the cell body. The series of fast movements leading to the emergence of activated ascospores from their shells was termed spore eclosion. Eclosion was a necessary initial step of germination, but eclosion without germ-tube production could be obtained by cycloheximide treatment. Major changes involved in eclosion occurred within a few seconds, some minutes after discharge of ascospores onto the host material (Fagus sylvatica). We postulate the existence of a host-derived, diffusible, specific factor eliciting those changes. This sophisticated recognition mechanism indicates a high degree of specialization of H. fragiforme to its endophytic symbiosis with beech trees. Key words: eclosion, tree, Fagus, Hypoxylon, host–fungus recognition.
Anatomie des feuilles dans les pousses polycycliques du Hêtre européen (Fagus sylvatica)
Authors: Thiébaut B. , Comps B. , Plancheron F.
Published: June 2008

The anatomical characters of European beech primary and secondary leaves (Fagus sylvatica L.) on polycyclic shoots obtained under various light conditions for 2 consecutive years were analyzed. Young plants were exposed to two luminosities, shade and light, which correspond to 20 and 80% of incident light, respectively. Shoots were grown under four light conditions during the 2 years: always in the shade, always in the light, in the shade during the 1st year and in the light during the 2nd year, and vice versa. The anatomical characters of leaves depend on both light intensity and cycle. Characters of secondary leaves vary more than those of primary leaves according to the light treatment. The effect of the luminosity applied during the 2nd year is more pronounced on secondary leaves. The cycle influence and the advantages brought by such a complex development are discussed. Key words: anatomy, leaves, light, polycyclism, beech.
Effects of side slope on low-volume road pavement performance: a full-scale assessment
Authors: Korkiala-Tanttu Leena , Dawson Andrew
Published: June 2008

The study concerns the full-scale testing of some low-volume road pavements using the heavy vehicle simulator (HVS) Nordic. The road structures were built with different angle side slopes and then trafficked to determine their performance. Performance was assessed in terms of rutting development and in terms of a geotechnical wedge stability method. A geometric factor has been introduced to describe the effect of side slope on the rate of rutting development. The geometric factor describes an average, structurally independent increase in the rate of rutting, which depends on the steepness of slope and on the distance to the edge of the construction but not on the load. To achieve the analysis, a finite element model of the road structures was established using appropriate resilient moduli values. These values were obtained after a comparison of values obtained from in situ measurements, back-calculated from in situ loading tests and laboratory tests, which differed appreciably.
Application of rock mass classification techniques to weak rock masses: A case study from the Ruahine Range, North Island, New Zealand
Authors: Brook Martin S. , Hutchinson Erin
Published: June 2008

Rock mass classification systems were first generated for use in engineering applications, but their potential for utilization in geomorphic studies has since been recognized. These techniques were mostly developed for hard rock environments, and questions remain about their applicability to weak rocks. Here, the applicability of three rock mass classification techniques (rock mass strength (RMS), rock mass rating (RMR), and slope mass rating (SMR)) to weak rock masses was analyzed. Techniques incorporated parameters such as uniaxial compressive rock strength, discontinuity condition and orientation, and groundwater ratings. Rock mass classification values were determined from 14 profiles sited on recently excavated road cuttings on the Saddle Road, in the Ruahine Range, North Island, New Zealand. This is an important transport route across the North Island’s axial ranges, with the road excavated into weak late Pliocene – Early Pleistocene mudstone. Mean slope and minimum slope angle were measured at each profile in concert with the rock mass classification schemes. The three classification techniques all appear to have limited usefulness given the subaerial conditions prevalent at the study site. It would appear that the relative weightings of the different parameters within the RMR, RMS, and SMR classification schemes would need modifying for weak rock masses, but the precise details of this are difficult to determine.
Channeling during settling and self-weight consolidation of cohesive sediments
Authors: Nam Soonkie , Gutierrez Marte , Diplas Panayiotis
Published: June 2008

As a part of the settling and self-weight consolidation of fine-grained materials, a common but not widely recognized phenomenon randomly occurs, namely channeling or the formation of narrow vertical paths or “channels.” Channel formation can have important effects on the microstructure, consolidation, and shear strength characteristics of newly formed sediments. However, only a few studies have been performed on channeling. The causes of channel formation and the factors affecting it are still not fully understood. This paper presents the results of an experimental study of channel formation during settling and self-weight consolidation in fine-grained materials. Four types of fine-grained materials and different slurry concentrations were tested using large and small settling columns, and channel formation was observed using a high-resolution digital camera. The results indicate that the primary mechanism for channel formation is the coalescence of small-scale discontinuities between clusters of soil particles formed by flocculation. The stronger the degree of flocculation, the more prevalent is the formation of channels. Pore pressure measurements show the effects of channels in dissipating excess pore pressures in sediments undergoing self-weight consolidation.
Ocean sediments—a study relating geophysical, geotechnical, and acoustic properties
Authors: Dunsiger A. D. , Chari T. R. , Fader G. B. , Peters G. R. , Simpkin P. G. , Zielinski A.
Published: June 2008

A multi-device high density survey of the seafloor was conducted in the outer Placentia Bay area of Newfoundland using the Bedford Institute of Oceanography research ship CSS Hudson. The acoustic records obtained from various systems, the seafloor soil samples collected by a piston corer and a grab sampler, and the in-situ data from a free-fall penetrometer were all subsequently analyzed. The correlation between the results of these different analyses is examined in this paper.
Techniques d'essais en chantier et en laboratoire pour la conception des fondations ancrées à la roche
Authors: Ballivy Gérard , Poulin Bernard , Guertin Jacques , Corriveau Roger
Published: June 2008

New transmission line towers in the Montreal area will be erected on caissons drilled in soil and in sedimentary rock (shale and shaly limestone). The St. Lawrence River crossing calls for very high towers, more than 85 m high, founded on four caissons drilled in alluviums and shales, or on concrete foundations anchored in bedrock. The vertical loads are estimated to be a maximum of 3.1 MN and the bending moments can be more than 42 MN∙m. Since these loading conditions are severe for this kind of rock, a shaly highly jointed rock, it was decided to investigate the rock properties in detail. Routine testing such as triaxial and direct shear tests in the lab, and pressuremeter, Goodman jack, and Packer tests on the site were carried out. But the most important concern in the project was to evaluate the shearing resistance between cement mortar and rock. The bonding stress was evaluated in the laboratory by a new type of pull-test: single untensioned tendons grouted in NX core samples. These tests enabled us to evaluate the bonding shear stress at many intervals along the projected embedment length and, also, to simulate the actual loading conditions. Fourteen pull-out tests were also performed on the sites in NX boreholes with Dywidag rods grouted in sound and fractured rock. Thus it was possible to evaluate the bonding strength available depending on the type of rock and the loading conditions.
Comparison of fabric sheet-reinforced earth design methods
Authors: Nicholls R. L.
Published: June 2008

The Coulomb failure plane method of design is compared with a sliding block design method for fabric sheet-reinforced retaining walls. The quantities of anchorage material required by the two design methods are calculated. Bench model tests are used to compare the surcharge loads resisted by given quantities of anchorage material distributed over a range of geometries between those indicated by these two design methods.
Prediction of frost heave in the laboratory during transient freezing
Authors: Konrad J.-M. , Morgenstern N. R.
Published: June 2008

Previous studies have demonstrated that, close to steady-state conditions, the ratio of the water intake velocity to the temperature gradient across the frozen fringe, called the segregation potential, is an important property characterizing a freezing soil. Under the more general conditions of transient freezing it is shown that the freezing characteristics of a given soil under zero applied load are defined by the segregation potential, the suction at the frozen–unfrozen interface, and the rate of cooling of the frozen fringe. These parameters form a relationship called the characteristic frost heave surface that can be used to predict mass transfer during the freezing of fine-grained soils. Examples of freezing tests conducted under various conditions are reproduced numerically to illustrate the fundamental character of this surface.
The Gronlid crossing, Saskatchewan Provincial Highway No. 6 at the Saskatchewan River
Authors: Lldgren R. A. , Sauer E. Karl
Published: June 2008

A traffic connection between Regina and the northeastern part of Saskatchewan required a crossing of the Saskatchewan River north of Gronlid. Slope instability developed in lacustrine and deltaic sands on the approaches to a ferry site installed in the early 1960s. Alternative ferry sites were considered but a river hydraulics study showed that other sites would not offer any improvement. The creation of a reservoir by projected dam at Nipawin and potential mining development in the area added incentive for the construction of a bridge to replace the original ferry installation.Valuable information was obtained from the ferry site for locating the new bridge and designing the approach roadways. It was possible to locate the bridge and approaches to minimize seepage, foundation, and slope instability problems in a deposit of over 100 m of saturated interbedded deltaic sand, lacustrine silt, and clay. A major artesian groundwater system was found in the bedrock sand of the Swan River Group, whereas groundwater conditions in the surficial stratified drift were mainly hydrostatic.The regional geology was used as a basis for detailed stratigraphic analysis at the site. The stratigraphy consisted of Lower Cretaceous sand and clay shale units underlying a dense unoxidized till. The site geology was divided into three parts: (1) the south valley approach, (2) the river channel crossing, and (3) the north valley approach. The bridge was completed in the summer of 1980.
Mineral–water interactions and their influence on the physical behavior of highly compacted Na bentonite
Authors: Pusch Roland
Published: June 2008

Na bentonite is the active component of one of the engineered barriers that are being considered in Sweden to surround the final disposal sites of radioactive wastes from nuclear reactors. It has been chosen because of its low permeability and ion diffusivity and of its self-healing ability through swelling. These properties are due to mineral–water interactions that yield a microstructural pattern with very narrow passages and a low average mobility of interparticle water molecules at high bulk densities.
Influence de surcharges concentrées sur la stabilité des talus
Authors: Tenier Pierre , Morlier Pierre
Published: June 2008

Concentrated loads, in particular when horizontal, are not properly taken into account in the simple methods of slope stability analysis such as Bishop's method. It is therefore proposed to replace in Bishop's equations any surcharge by a statically equivalent stress distribution on the failure surface. For reasons of simplicity, this distribution is taken according to Flamant, slightly modified to fit stress distributions obtained from finite element studies. An application is presented in the form of the optimization of a slope stabilization by tie-backs. [Journal translation]
Comparisons of deformation characteristics of rockfill materials using monotonic and cyclic loading laboratory tests and in situ tests
Authors: Yasuda Nario , Matsumoto Norihisa
Published: June 2008

The deformation characteristics of rockfill materials at very small strains were investigated by comparing the results of monotonic and cyclic loading laboratory tests with geophysical P- and S-wave logging data from the field. Using a precision linear variable differential transformer for displacement, the elastic moduli of rockfill materials at very small strains were measured in monotonic and cyclic loading triaxial tests. The laboratory test results agreed well with the field results. The shear moduli of rockfill materials from both a monotonic loading torsional simple shear test and a cyclic loading torsional simple shear test also showed good correspondence. Furthermore, the shear modulus predicted from the in situ shear wave tests in rockfill dams corresponded reasonably well with the modulus in the large-scale triaxial tests in the laboratory. Key words : deformation characteristics, embankment dams, rockfill materials, laboratory test, in situ test.
Long-term field study of a deep-corrugated metal box type culvert
Authors: Sargand Shad M. , Hazen Glenn A. , Masada Teruhisa , Hurd John O.
Published: June 2008

A deep-corrugated metal box culvert structure was instrumented with strain gages and tape extensometer reference points in the field. Performance was monitored during backfilling and, paving and under static loads shortly after completion of installation. Beyond the initial study, deflection readings were taken periodically for 3 years. Also, the static load test was conducted during the second and third years to examine changes in structural responses over time. The results of the study showed that the culvert deflection stabilized within the 3 year period. The overall deflection recorded during the construction phases was about 2 cm, and the additional deflection of about 0.8 cm took place during the long-term study period. The deflection, moment, and thrust responses of the culvert under static loads improved over time. This was considered to be because of backfill soil densification under repeated traffic loads. Key words : long-term field performance, culvert, box type, deep corrugation, deflection, live loads.
Sixteenth Canadian Geotechnical Colloquium: Frost heave in soils: concepts and engineering
Authors: Konrad J.-M.
Published: June 2008

Frost heave in soils is analysed from a fundamental point of view to predict the development of periodic ice lens formation that is observed in frozen soils. A model of simultaneous heat and mass transfer associated with three new concepts is described and was found to exhibit many of the frost heave features observed in laboratory tests. An efficient frost heave parameter termed the segregation potential, SP, is also described and found to be an adequate input to a general formulation of heat and mass transfer for the prediction of frost heave in soils for both laboratory and field conditions. Representative values of SP depend on the stress and thermal histories of the soil deposit. The SP-based approach can be used for solving two-dimensional frost heave problems and yields stress, temperature, and ice-content distributions with time. Key words : frost heave, soils, segregation potential, simulation, thermodynamics.
Landslide risk assessment and acceptable risk
Authors: Fell Robin
Published: June 2008

Definitions for risk and hazard which are suited to landslide risk assessment are presented. Acceptable risk is discussed in relation to other risks accepted by the community, and acceptable specific risks are proposed, depending on whether the landsliding is natural or sliding of a man-made slope. Methods for quantifying the risk are discussed, and qualitative definitions are suggested for use when these are desirable. Examples are given of use of risk assessment in areas affected by landsliding and debris flows. Key words : landsliding, slope stability, risk assessment.
Frost heave characteristics of undisturbed sensitive Champlain Sea clay
Authors: Konrad J.-M. , Seto J.T.C.
Published: June 2008

Undisturbed Champlain Sea clay samples were subjected to laboratory freezing tests with pore-pressure measurements in order to determine the freezing characteristics of a structured compressible soil. Step-freezing and ramped-freezing tests with applied back pressure were conducted on 10 cm high samples in open-system conditions. Significant pore-pressure reductions in the unfrozen soil induce important frost-induced consolidation and destructuration of the clay. It was found that the freezing characteristics of Saint-Alban clay are best defined by the segregation potential at the active ice lens, SPℓ, which includes water fluxes generated within the frozen fringe and within the unfrozen soil as excess water is expelled during consolidation, and finally water from an external source. For the Saint-Alban clay, SPℓ values of the intact clay ranged between 450 and 600 × 10−5 mm2/(s °C), whereas those of destructured clay at a lower void ratio were significantly smaller. Back-calculating the segregation potential solely from surface heave measurements in laboratory tests may underestimate considerably the frost susceptibility of compressible structured clays. Segregation potential inferred from instrumented field sites was 430 × 10−5 mm2/(s °C) and is consistent with the laboratory tests results. Key words : freezing, frost heave, structured clay, undisturbed, consolidation.
A column study of static nonequilibrium fluid pressures in sand during prolonged drainage
Authors: Barbour S. Lee , Yanful Ernest K.
Published: June 2008

In the design of layered soil systems, such as the design of liners or covers over unsaturated soil, a key design concern is the magnitude of negative fluid pressure that will develop along the base of the liner or cover. In the absence of evaporation or vapour migration, the maximum negative fluid pressures will develop near the cessation of drainage. Previous theoretical analyses and numerical modelling of these systems have indicated that this pressure will be the pressure at which an underlying sand reaches its residual water content. The hydraulic conductivity of the sand at these pressures is so small that "static" nonequilibrium pressures are sustained over long periods of time. In this note, laboratory verification is provided for the magnitude of these pressures based on drainage of a fine and coarse sand column. Key words : covers, liners, air-entry value, residual saturation, layering, drainage.
The effect of dynamic loading on lateral stress in sand
Authors: Zhu Fanyu , Clark Jack I.
Published: June 2008

This paper presents the results of a laboratory study on the lateral stress in a vibrated sand. No. 3 Ottawa sand was tested on a snaking table providing vertical vibration, and at-rest lateral stress was measured using a modified oedometer ring. The test results show that the lateral stress in normally consolidated sand increases with vibration time. The magnitude of the increase in lateral stress is related to the density of sand and the intensity of vibration. For overconsolidated sand with a high coefficient of earth pressure at rest, the lateral stress decreases with vibration time. Stress paths of a tested specimen are also presented in this paper. Key words : sand, coefficient of earth pressure at rest, lateral stress, vibration, overconsolidation ratio, stress path.
Synthesis, X-ray structure, and binding properties of a new fluorescent molecular clip derived from diethoxycarbonyl glycoluril
Authors: Hu Sheng-Li , Yin Guo-Dong , Wang Yu-Zhou , Wu An-Xin
Published: June 2008

A new fluorescent molecule clip derived from diethoxycarbonyl glycoluril with two 2,5-diphenyl-furan sidewalls was designed and synthesized. Its structure and conformation was confirmed by single-crystal X-ray diffraction. Its binding properties, investigated by fluorescence spectroscopey, showed that it can selectively bind Fe3+ with fluorescence quenching.Key words: diethoxycarbonyl glycoluril, molecular clip, fluorescence, Fe(III).
Exploring the reaction of formaldehyde with α-N-protected amino acid hydrazides
Authors: Verardo Giancarlo , Geatti Paola , Mancuso Marta , Strazzolini Paolo
Published: June 2008

The reaction of formaldehyde with enantiomerically pure α-N-protected amino acid hydrazides is described. The system has been investigated in different solvents, including both aqueous formaldehyde and paraformaldehyde, with the aim of simplifying the final reaction mixture. Aqueous formaldehyde in refluxing THF proved to be the best combination, affording mainly the corresponding monomeric N-methylene and 1,3,5-trisubstituted-1,3,5-hexahydrotriazine derivatives. The monomeric form was the only one present at high temperature, as evidenced by1H and13C NMR spectroscopy.Key words: amino acid hydrazides, formaldehyde, condensation reactions, monomeric N-methylene derivatives, oligomers.
MECHANICAL VIBRATION AND BUCKLING ANALYSIS OF FGM PLATES AND SHELLS USING A FOUR-NODE QUASI-CONFORMING SHELL ELEMENT
Authors: HAN SUNG-CHEON , LOMBOY GILSON RESCOBER , KIM KI-DU
Published: June 2008

In this paper, we investigate the natural frequencies and buckling loads of functionally graded material (FGM) plates and shells, using a quasi-conforming shell element that accounts for the transverse shear strains and rotary inertia. The eigenvalues of the FGM plates and shells are calculated by varying the volume fraction of the ceramic and metallic constituents using a sigmoid function, but the Poisson ratios of the FGM plates and shells are assumed to be constant. The expressions for the membrane, bending and shear stiffness of FGM shell elements are more a complicated combination of material properties than a homogeneous element. In order to validate the finite element numerical solutions, the Navier solutions for rectangular plates based on the first order shear deformation theory are also presented. The present numerical solutions for composite and sigmoid FGM (S-FGM) plates and shells are verified by the Navier solutions and various examples of composite and FGM structures. The present results are in good agreement with the Navier theoretical solutions.
Short- and long-term effects of (−)-epicatechin on myocardial ischemia-reperfusion injury
Authors: Yamazaki Katrina Go , Romero-Perez Diego , Barraza-Hidalgo Maraliz , Cruz Michelle , Rivas Maria , Cortez-Gomez Brenda , Ceballos Guillermo , Villarreal Francisco
Published: June 2008

Epidemiological studies have shown a correlation between flavonoid-rich diets and improved cardiovascular prognosis. Cocoa contains large amounts of flavonoids, in particular flavanols (mostly catechins and epicatechins). Flavonoids possess pleiotropic properties that may confer protective effects to tissues during injury. We examined the ability of epicatechin to reduce short-and long-term ischemia-reperfusion (I/R) myocardial injury. Epicatechin (1 mg·kg−1·day−1) pretreatment (Tx) was administered daily via oral gavage to male rats for 2 or 10 days. Controls received water. Ischemia was induced via a 45-min coronary occlusion. Reperfusion was allowed until 48 h or 3 wk while Tx continued. We measured infarct (MI) size (%), hemodynamics, myeloperoxidase activity, tissue oxidative stress, and matrix metalloproteinase-9 (MMP-9) activity in 48-h groups. Cardiac morphometry was also evaluated in 3-wk groups. With 2 days of Tx, no reductions in MI size occurred. After 10 days, a significant ∼50% reduction in MI size occurred. Epicatechin rats demonstrated no significant changes in hemodynamics. Tissue oxidative stress was reduced significantly in the epicatechin group vs. controls. MMP-9 activity demonstrated limited increases in the infarct region with epicatechin. By 3 wk, a significant 32% reduction in infarct size was observed with Tx, accompanied with sustained hemodynamics and preserved chamber morphometry. In conclusion, epicatechin Tx confers cardioprotection in the setting of I/R injury. The effects are independent of changes in hemodynamics, are sustained over time, and are accompanied by reduced levels of indicators of tissue injury. Results warrant the evaluation of cocoa flavanols as possible therapeutic agents to limit ischemic injury.
An excitatory role for peripheral EP3 receptors in bladder afferent function
Authors: Su Xin , Lashinger Erin S. R. , Leon Lisa A. , Hoffman Bryan E. , Hieble J. Paul , Gardner Scott D. , Fries Harvey E. , Edwards Richard M. , Li Jun , Laping Nicholas J.
Published: June 2008

The excitatory roles of EP3 receptors at the peripheral afferent nerve innervating the rat urinary bladder have been evaluated by using the selective EP3 antagonist (2 E)-3-{1-[(2,4-dichlorophenyl)methyl]-5-fluoro-3-methyl-1 H-indol-7-yl}- N-[(4,5-dichloro-2-thienyl)sulfonyl]-2-propenamide (DG-041). The bladder rhythmic contraction model and a bladder pain model measuring the visceromotor reflex (VMR) to urinary bladder distension (UBD) have been used to evaluate DG-041 in female rats. In addition, male rats [spontaneously hypertensive rat (SHR), Wistar-Kyoto (WKY), and Sprague-Dawley (SD)] were anesthetized with pentobarbital sodium, and primary afferent fibers in the L6 dorsal root were isolated for recording the inhibitory response to UBD following intravenous injection of DG-041. Intravenous injection of DG-041 (10 mg/kg), a peripherally restricted EP3 receptor antagonist, significantly reduced the frequency of bladder rhythmic contraction and inhibited the VMR response to bladder distension. The magnitude of reduction of the VMR response was not different in the different strains of rats (SD, SHR, and WKY). Furthermore, quantitative characterization of the mechanosensitive properties of bladder afferent nerves in SHR, WKY, and SD rats did not show the SHR to be supersensitive to bladder distension. DG-041 selectively attenuated responses of mechanosensitive afferent nerves to UBD, with strong suppression on the slow-conducting, high-threshold afferent fibers, with equivalent activity in the three strains. We conclude that sensitization of afferent nerve activity was not one of the mechanisms of bladder hypersensitivity in SHR. EP3 receptors are involved in the regulation of bladder micturition and bladder nociception at the peripheral level.
A micro-CT analysis of murine lung recruitment in bleomycin-induced lung injury
Authors: Shofer Scott , Badea Cristian , Qi Yi , Potts Erin , Foster W. Michael , Johnson G. Allan
Published: June 2008

The effects of lung injury on pulmonary recruitment are incompletely understood. X-ray computed tomography (CT) has been a valuable tool in assessing changes in recruitment during lung injury. With the development of preclinical CT scanners designed for thoracic imaging in rodents, it is possible to acquire high-resolution images during the evolution of a pulmonary injury in living mice. We quantitatively assessed changes in recruitment caused by intratracheal bleomycin at 1 and 3 wk after administration using micro-CT in 129S6/SvEvTac mice. Twenty female mice were administered 2.5 U of bleomycin or saline and imaged with micro-CT at end inspiration and end expiration. Mice were extubated and allowed to recover from anesthesia and then reevaluated in vivo for quasi-static compliance measurements, followed by harvesting of the lungs for collagen analysis and histology. CT images were converted to histograms and analyzed for mean lung attenuation (MLA). MLA was significantly greater for bleomycin-exposed mice at week 1 for both inspiration ( P < 0.0047) and exhalation ( P < 0.0377) but was not significantly different for week 3 bleomycin-exposed mice. However, week 3 bleomycin-exposed mice did display significant increases in MLA shift from expiration to inspiration compared with either group of control mice ( P < 0.005), suggesting increased lung recruitment at this time point. Week 1 bleomycin-exposed mice displayed normal shifts in MLA with inspiration, suggesting normal lung recruitment despite significant radiographic and histological changes. Lung alveolar recruitment is preserved in a mouse model of bleomycin-induced parenchymal injury despite significant changes in radiographic and physiological parameters.
Chk1 and Chk2 are differentially involved in homologous recombination repair and cell cycle arrest in response to DNA double-strand breaks induced by camptothecins
Authors: Huang Min , Miao Ze-Hong , Zhu Hong , Cai Yu-Jun , Lu Wei , Ding Jian
Published: June 2008

Camptothecins (CPT) activate S or G2-M arrest and the homologous recombination (HR) repair pathway in tumor cells. In this process, both checkpoint kinases 1 and 2 (Chk1 and Chk2, respectively) are activated, but their differential roles, especially in the coordination of checkpoint and repair control, and potential clinic relevance remain to be fully elucidated. In this study, the repairable double-strand breaks were induced in human colon cancer HCT116 cells by 1-h exposure to 25 or 100 nmol/L CPT and its novel derivative chimmitecan. The cellular disposal of double-strand breaks was reflected as the progressive dispersal of γ-H2AX foci, reduction of “comet” tails, dynamic activation of RAD51-mediated HR repair, and reversible G2-M arrest. In this model, the differential kinetics of Chk1 and Chk2 activation was characterized by the progressively increased phosphorylation of Chk2 until 72 h, the degradation of Chk1, and the disappearance of phosphorylated Chk1 48 h after drug removal. Using RNA interference, we further showed that Chk2 was essential to G2-M arrest, whereas Chk1 was mainly required for HR repair in CPT-treated HCT116 cells. Moreover, Chk2, rather than Chk1, predominated over the control of cell survival in this model. The differential roles of Chk1 and Chk2 in regulating HR repair and G2-M phase arrest were also confirmed in HT-29 colon cancer cells. Together, these findings systematically dissect the differential roles of Chk1 and Chk2 in a favorable model pursuing CPT-driven DNA damage responses, providing critical evidence to further explore checkpoint modulation, especially Chk2 inhibition as a therapeutic strategy in combination with CPT. [Mol Cancer Ther 2008;7(6):1440–9]
Recombinant, refolded tetrameric p53 and gonadotropin-releasing hormone-p53 slow proliferation and induce apoptosis in p53-deficient cancer cells
Authors: LaFevre-Bernt Michelle , Wu Shili , Lin Xinli
Published: June 2008

The p53 tumor suppressor is mutated in over 50% of human cancers. Mutations resulting in amino acid changes within p53 result in a loss of activity and consequent changes in expression of genes that regulate DNA repair and cell cycle progression. Replacement of p53 using protein therapy would restore p53 function in p53-deficient tumor cells, with a consequence of tumor cell death and tumor regression. p53 functions in a tetrameric form in vivo. Here, we refolded a wild-type, full-length p53 from inclusion bodies expressed in Escherichia coli as a stable tetramer. The tetrameric p53 binds to p53-specific DNA and, when transformed into a p53-deficient cancer cell line, induced apoptosis of the transformed cells. Next, using the same expression and refolding technology, we produced a stable tetramer of recombinant gonadotropin-releasing hormone-p53 fusion protein (GnRH-p53), which traverses the plasma membrane, slows proliferation, and induces apoptosis in p53-deficient, GnRH-receptor–expressing cancer cell lines. In addition, we showed a time-dependent binding and internalization of GnRH-p53 to a receptor-expressing cell line. We conclude that the GnRH-p53 fusion strategy may provide a basis for constructing an effective cancer therapeutic for patients with tumors in GnRH-receptor–positive tissue types. [Mol Cancer Ther 2008;7(6):1420–9]
17-Acetoxyjolkinolide B irreversibly inhibits IκB kinase and induces apoptosis of tumor cells
Authors: Yan Shou-Sheng , Li Ying , Wang Ying , Shen Shen-Si , Gu Yuan , Wang Hong-Bing , Qin Guo-Wei , Yu Qiang
Published: June 2008

Nuclear factor-κB (NF-κB) is critically important for tumor cell survival, growth, angiogenesis, and metastasis. One of the key events in the NF-κB signaling is the activation of inhibitor of NF-κB kinase (IKK) in response to stimuli of various cytokines. We have identified 17-acetoxyjolkinolide B (17-AJB) from a traditional Chinese medicinal herb Euphorbia fischeriana Steud as a novel small-molecule inhibitor of IKK. 17-AJB effectively inhibited tumor necrosis factor-α–induced NF-κB activation and induced apoptosis of tumor cells. 17-AJB had no effect on binding of tumor necrosis factor-α to its receptor or on binding of NF-κB to DNA. It inhibited NF-κB nuclear translocation. Detailed analysis revealed that the direct target of 17-AJB was IKK. 17-AJB kept IKK in its phosphorylated form irreversibly. This irreversible modification of IKK inactivated its kinase activity, leading to its failure to activate NF-κB. The effect of 17-AJB on IKK was specific. It had no effect on other kinases such as p38, p44/42, and JNK. In addition, 17-AJB induced apoptosis in tumor cells. The effects of 17-AJB on apoptosis correlated with inhibition of expression of the NF-κB-regulated genes. Taken together, our data suggest that 17-AJB is a novel type NF-κB pathway inhibitor. Its unique interaction mechanism with IKK may render it a strong apoptosis inducer of tumor cells and a novel type anticancer drug candidate. [Mol Cancer Ther 2008;7(6):1523–32]
Senescence-Dependent MutSα Dysfunction Attenuates Mismatch Repair
Authors: Chang In-Youb , Jin Ming , Yoon Sang Pil , Youn Cha-Kyung , Yoon Young , Moon Sung-Pyo , Hyun Jin-Won , Jun Jae Yeoul , You Ho Jin
Published: June 2008

DNA damage and mutations in the genome increase with age. To determine the potential mechanisms of senescence-dependent increases in genomic instability, we analyzed DNA mismatch repair (MMR) efficiency in young and senescent human colonic fibroblast and human embryonic lung fibroblast. It was found that MMR activity is significantly reduced in senescent cells. Western blot and immunohistochemistry analysis revealed that hMSH2 and MSH6 protein (MutSα complex), which is a known key component in the MMR pathway, is markedly down-regulated in senescent cells. Moreover, the addition of purified MutSα to extracts from senescent cells led to the restoration of MMR activity. Semiquantitative reverse transcription-PCR analysis exhibited that MSH2 mRNA level is reduced in senescent cells. In addition, a decrease in E2F transcriptional activity in senescent cells was found to be crucial for MSH2 suppression. E2F1 small interfering RNA expression reduced hMSH2 expression and MMR activity in young human primary fibroblast cells. Importantly, expression of E2F1 in quiescent cells restored the MSH2 expression as well as MMR activity, whereas E2F1-infected senescent cells exhibited no restoration of MSH2 expression and MMR activity. These results indicate that the suppression of E2F1 transcriptional activity in senescent cells lead to stable repression of MSH2, followed by a induction of MutSα dysfunction, which results in a reduced cellular MMR capacity in senescent cells. (Mol Cancer Res 2008;6(6):978–89)
Multiple Signaling Pathways Are Responsible for Prostaglandin E2–Induced Murine Keratinocyte Proliferation
Authors: Ansari Kausar M. , Rundhaug Joyce E. , Fischer Susan M.
Published: June 2008

Although prostaglandin E2 (PGE2) has been shown by pharmacologic and genetic studies to be important in skin cancer, the molecular mechanism(s) by which it contributes to tumor growth is not well understood. In this study, we investigated the mechanisms by which PGE2 stimulates murine keratinocyte proliferation using in vitro and in vivo models. In primary mouse keratinocyte cultures, PGE2 activated the epidermal growth factor receptor (EGFR) and its downstream signaling pathways as well as increased cyclic AMP (cAMP) production and activated the cAMP response element binding protein (CREB). EGFR activation was not significantly inhibited by pretreatment with a c-src inhibitor (PP2), nor by a protein kinase A inhibitor (H-89). However, PGE2-stimulated extracellularly regulated kinase 1/2 (ERK1/2) activation was completely blocked by EGFR, ERK1/2, and phosphatidylinositol 3-kinase (PI3K) pathway inhibitors. In addition, these inhibitors attenuated the PGE2-induced proliferation, nuclear factor-κB, activator protein-1 (AP-1), and CREB binding to the promoter regions of the cyclin D1 and vascular endothelial growth factor (VEGF) genes and expression of cyclin D1 and VEGF in primary mouse keratinocytes. Similarly, in vivo, we found that WT mice treated with PGE2 and untreated cyclooxygenase-2–overexpressing transgenic mice had higher levels of cell proliferation and expression of cyclin D1 and VEGF, as well as higher levels of activated EGFR, nuclear factor-κB, AP-1, and CREB, than vehicle-treated WT mice. Our findings provide evidence for a link between cyclooxygenase-2 overexpression and EGFR-, ERK-, PI3K-, cAMP-mediated cell proliferation, and the tumor-promoting activity of PGE2 in mouse skin. (Mol Cancer Res 2008;6(6):1003–16)
Dietary Eicosapentaenoic Acid and Docosahexaenoic Acid Are More Effective than Alpha-Linolenic Acid in Improving Insulin Sensitivity in Rats
Authors: Andersen Gaby , Harnack Kerstin , Erbersdobler Helmut F. , Somoza Veronika
Published: June 2008

In the present study, we investigated whether long-term administration of high dose of α-linolenic acid (ALA) is able to mimic the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) or a mixture of both with respect to insulin sensitivity in male Wistar rats. Furthermore, we intended to test whether these n–3 polyunsaturated fatty acids reveal differential effects on glucose and insulin levels. As a result, plasma glucose and insulin levels were lowered by 35 and 38%, respectively, in the EPA and DHA group compared to the ALA group. Insulin sensitivity was substantially improved, as indicated by a 60% decreased HOMA index after an 8-week EPA and DHA administration, as compared to the effect observed for feeding ALA. However, insulin sensitivity did not differ between animals of the EPA and the DHA group. These results demonstrate that ALA intake at the expense of EPA and DHA in a diet high in n–3 fatty acids does not represent an alternative to raising oily fish consumption with regard to insulin sensitivity. Furthermore, a differential effect of the members of the n–3 family was shown for ALA compared to EPA and DHA, but EPA and DHA revealed comparable effects on insulin sensitivity.
Fibroblast Growth Factor Receptor and Platelet-Derived Growth Factor Receptor Abnormalities in Eosinophilic Myeloproliferative Disorders
Authors: Cross Nicholas C.P. , Reiter Andreas
Published: June 2008

Rearrangements of the genes encoding the fibroblast growth factor receptor 1 (FGFR1) and platelet-derived growth factor receptors (PDGFR) α or β receptor tyrosine kinases are found in a rare but important subset of patients with atypical myeloproliferative disorders that are usually but not always associated with eosinophilia. Chromosomal translocations or other rearrangements at 8p11–12, 4q12 or 5q31–33 give rise to diverse fusion genes encoding chimaeric proteins with constitutive transforming activity. There is considerable molecular heterogeneity with 8 partner genes currently known for FGFR1, 6 for PDGFRA and 17 for PDGFRB. The vast majority of patients with PDGFRA or PDGFRB fusions achieve rapid and durable complete haematological and molecular responses to sustained imatinib therapy. A key ongoing challenge is to define the molecular pathogenesis of the great majority of atypical myeloproliferative disorders for whom the causative lesion remains unknown, since very few of these cases gain any benefit from imatinib or other second-generation inhibitors.
RAS Pathway Mutations in Juvenile Myelomonocytic Leukemia
Authors: Emanuel Peter D.
Published: June 2008

Juvenile myelomonocytic leukemia (JMML) is a rare blood cell malignancy occurring in very young children. Yet, just as has been proven in other rare diseases, the study of JMML has provided us great insights into aberrant and dysregulated signal transduction through the Ras pathway, with the ultimate development of malignancy. Further, JMML investigations have also revealed to us much about the genetic predisposition to cancer.