bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of LH receptor mRNA splice variants in bovine granulosa cells: changes with follicle size and regulation by FSH in vitro
Authors: Nogueira M.F.G. , Buratini J. , Price C.A. , Castilho A.C.S. , Pinto M.G.L. , Barros C.M. 
Published: December 2006

AbstractIn cattle, most evidence suggests that granulosa cells express LH receptors (LHR) after (or as) the follicle becomes dominant, however there is some suggestion that granulosa cells from smaller pre‐dominant follicles may express several LHR mRNA splice variants. The objective of this study was to measure LHR expression in bovine follicles of defined size and steroidogenic ability, and in granulosa cells from small follicles (<6 mm diameter) undergoing differentiation in vitro. Semiquantitative RT‐PCR demonstrated that LHR mRNA was undetectable in granulosa cells of follicles <7 mm diameter (nondominant follicles), and increased with follicle diameter in follicles >7 mm diameter. Splice variants with deletions of exon 10 and part of exon 11 were detected as previously described, and we detected a novel splice variant with a deletion of exon 3. Cultured granulosa cells contained LHR mRNA, but with significantly greater amounts of variants with deletions of exon 10 and/or exon 11 compared with cells from dominant follicles. FSH increased the abundance of some but not all LHR mRNA splice variants in cultured granulosa cells. The addition of LH to cultured cells did not increase progesterone secretion, despite the presence of LHR mRNA. Collectively, these data suggest that granulosa cells do not acquire functional LHR until follicle dominance occurs. Mol. Reprod. Dev. 74: 680–686, 2007. © 2006 Wiley‐Liss, Inc.
Follicular growth in vitro: detection of growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) during in vitro culture of ovine cortical slices
Authors: Mery Lionel , Lefevre Annick , Benchaib Mehdi , Demirci Banu , Salle Bruno , Guerin Jean‐Francois , Lornage Jacqueline 
Published: December 2006

AbstractPrimordial follicles from different mammal species can survive and enter the growth phase in vitro but do not develop beyond the primary stage. The hypothesis was that, in sheep, in vitro follicular growth is arrested because of a lack of secretion of GDF9 and/or BMP15. Cortical slices of 0.3–0.5 mm thickness issued from 5‐ to 6‐month‐old lambs were cultured for 15 days. The pieces were fixed on days 0, 2, 4, 7, 10, and 15 of culture. Follicle morphology, RT‐PCR exploration of GDF9 and BMP15 mRNA, immunohistochemical location of their proteins and their receptor BMPRIB and BMPRII were assessed at different time of culture. The mean percentage of primordial follicles decreased from 58.6% (day 0) to 13.4% (day 15) (P < 0.01), whereas that of primary follicles increased from 3.2% (day 0) to 31.5% on day 4 (P < 0.01), then remained stable until day 15 (35.6%). The percentage of atretic follicles increased from 14.7% (day 0) to 27.1% (day 15) (P < 0.05). A few secondary follicles were observed on days 4 and 10, representing 1.0%, and 2.1% of the total number of follicles. GDF9 and BMP15 mRNAs were detected from harvesting (day 0) up to day 15 following culture. At the same time, positive immunoreactions for GDF9, BMP15 and for BMPRIB and BMPRII were also found in oocyte cytoplasm. In conclusion, expression of GDF9, BMP15 and their receptors BMPRIB and BMPRII are detected during in vitro culture of ovine cortical slices. Mol. Reprod. Dev. 74: 767–774, 2007. © 2006 Wiley‐Liss, Inc.
Membrane progesterone receptor gamma: Tissue distribution and expression in ciliated cells in the fallopian tube
Authors: Nutu Magdalena , Weijdegård Birgitta , Thomas Peter , Bergh Christina , Thurin‐Kjellberg Ann , Pang Yefei , Billig Håkan , Larsson D.G. Joakim 
Published: December 2006

AbstractNon‐genomic, rapid actions of steroids have long been known, suggesting the possible presence of non‐classical steroid receptors. A membrane receptor for progestins (mPR) was recently described in the spotted seatrout, and transcripts of three related receptors (α, β, and γ) were subsequently identified in other species including human and mouse. To begin exploring the roles of mPRγ in mammals, we have generated an antibody against this receptor. The specificity of the antibody was demonstrated by both overexpression and RNA interference experiments. Using the antibody, we show that mPRγ is expressed in female mouse reproductive tissues such as ovary and fallopian tube, and also in the lung and liver of both sexes. Immunohistochemical studies revealed that mPRγ is associated with the apical membrane of ciliated cells facing the lumen of the fallopian tube. The presence of mPRγ in ciliated cells of the fallopian tube was also demonstrated in human samples. Rapid effects of progesterone on ciliary beat frequency in the fallopian tube have recently been reported. Together, this suggests a common role for mPRγ in the regulation of ciliary activity in the fallopian tube and thus gamete transport in mammals. The presence of mPRγ in lung and liver of mice suggests that the receptor mediates the actions of progesterone outside the reproductive tract as well. Mol. Reprod. Dev. 74: 843–850, 2007. © 2006 Wiley‐Liss, Inc.
Energy dissipation and post‐bifurcation behaviour of granular soils
Authors: Gutierrez M. , Vardoulakis I. 
Published: December 2006

AbstractExtensive experimental data indicate that plastic flow in granular materials is non‐coaxial (i.e. the principal directions of the plastic strain increment tensor and the stress tensor do not coincide) for loadings involving principal stress rotation. The degree of non‐coaxiality depends on the magnitude of principal stress rotation, hence plastic flow is also incrementally non‐linear. The paper presents an analysis and discussion of the effects of non‐coaxial plastic flow on the post‐bifurcation response of dilatant granular materials. Significant differences are observed between the energy dissipation and stress–dilatancy response of soils before and after shear‐band formation. These differences are attributed to the non‐coaxiality of plastic flow during post‐bifurcation shearing. In turn, the non‐coaxiality is attributed to principal stress rotation within the shear band, which is consistent with the assumption that the materials inside the shear undergo simple shear deformation. Experimental data are presented to support the analytical results. Copyright © 2006 John Wiley & Sons, Ltd.
Analytical formulas for the geometric and inertia quantities of the largest removable blocks around tunnels
Authors: Tonon Fulvio 
Published: December 2006

AbstractThis paper presents algorithms for determining the vertices of the maximum removable block (MB) created by a joint pyramid (JP) around a tunnel when discontinuities are fully persistent. It is shown that an MB cannot be formed by more than 4 discontinuities and this drastically limits the proliferation of rock blocks that need to be analysed. The non‐convex block obtained after the MB is tunnelled through (real maximum block, RMB) is partitioned into a set of tetrahedra, and procedures are given for determining the vertices of these tetrahedra. Geometric and inertia quantities needed for stability analysis and support/reinforcement design are determined as functions of the calculated vertices' co‐ordinates. These quantities are: RMB's volume, face areas, perimeter of the excavated surface, centroid and inertia tensor. The algorithms for their calculation are at least two times faster than other algorithms previously proposed in other applications. It is shown that the formulations presented by Goodman and Shi for translational analysis and by Tonon for rotatability analysis can be used to analyse the RMBs using the geometric quantities presented. A numerical example is presented among those used to verify these analytical procedures and their implementation. Copyright © 2006 John Wiley & Sons, Ltd.
A two‐scale approach for fluid flow in fractured porous media
Authors: Réthoré Julien , Borst René de , Abellan Marie‐Angèle 
Published: December 2006

AbstractA two‐scale numerical model is developed for fluid flow in fractured, deforming porous media. At the microscale the flow in the cavity of a fracture is modelled as a viscous fluid. From the micromechanics of the flow in the cavity, coupling equations are derived for the momentum and the mass couplings to the equations for a fluid‐saturated porous medium, which are assumed to hold on the macroscopic scale. The finite element equations are derived for this two‐scale approach and integrated over time. By exploiting the partition‐of‐unity property of the finite element shape functions, the position and direction of the fractures is independent from the underlying discretization. The resulting discrete equations are non‐linear due to the non‐linearity of the coupling terms. A consistent linearization is given for use within a Newton–Raphson iterative procedure. Finally, examples are given to show the versatility and the efficiency of the approach, and show that faults in a deforming porous medium can have a significant effect on the local as well as on the overall flow and deformation patterns. Copyright © 2006 John Wiley & Sons, Ltd.
In vitro bone engineering based on polycaprolactone and polycaprolactone–tricalcium phosphate composites
Authors: Zhou Yefang , Hutmacher Dietmar W , Varawan Sae‐Lim , Lim Tit Meng 
Published: December 2006

AbstractThe filling of bone defects in load‐bearing areas requires scaffolds possessing physical properties that are in the range of those of the host bone. In this report, composite scaffolds comprising medical‐grade polycaprolactone and tricalcium phosphate (mPCL‐TCP) (80:20), which have been designed for load‐bearing applications, are characterized and compared with mPCL scaffolds, using in vitro studies. The composite scaffolds exhibited improved hydrophilicity, compressive modulus and strength. Human alveolar osteoblasts (AOs) grown on the composite achieved higher seeding efficiencies and more uniform distribution when compared with mPCL preparations alone. AOs demonstrated better proliferation, denser multilayered cell‐sheets and showed earlier expression of bone matrix‐related proteins on the composite than on mPCL during 28 days in vitro culture. The calcium content in the media decreased in both scaffold/cell constructs. Alkaline phosphatase activity increased significantly in mPCL matrices after osteogenic induction but no distinct change was observed in the composite. Osteocalcin expression was down‐regulated by induction in the composite but was up‐regulated in mPCL at both RNA and protein level. Immuno‐reactive signals for osteopontin and collagen type I, in combination with mineral nodules were found to be stronger in mPCL‐TCP scaffolds. We conclude that the composite scaffolds were more hydrophilic and had improved mechanical properties over mPCL scaffolds. Moreover, the primary AOs achieved better cell proliferation, and showed earlier and different matrix protein expression patterns on the composite scaffolds than on the mPCL scaffolds. Copyright © 2006 Society of Chemical Industry
A novel approach for the preparation of acrylate–siloxane particles with core–shell structure
Authors: Cao Shunsheng , Liu Bailing , Deng Xiaobo , Luo Rong , Chen Hualin 
Published: December 2006

AbstractIt is well known that polysiloxane has excellent properties, such as water repellency, low surface energy, biocompatibility, etc. Its application, however, is subject to some limit due to poor cohesiveness and poor film‐forming properties. Recently, many efforts have been made to overcome such flaws. It is found that polyacrylate is in common consideration for its good cohesiveness and excellent film‐forming properties. This is why there have been so many descriptions of core–shell PSi–PA (PSi, polysiloxane as core; PA, polyacrylate as shell) particles in the literature. Unfortunately, their hydrophobicity is considerably different; therefore, the reversed morphological PA–PSi particles are scarcely available. In the work reported here, core‐shell PA–PSi structures with poly(butyl methacrylate) (PA) as the core and PSi as the shell were successfully prepared by dispersion polymerization. Characterization of the PA–PSi particles was carried out using transmission electron microscopy, particle size analysis, X‐ray photoelectron spectroscopy and static contact angle measurements. Copyright © 2006 Society of Chemical Industry
Fluorescent polyelectrolytes as protein sensors
Authors: Ambade Ashootosh Vasant , Sandanaraj Britto Selvaraj , Klaikherd Akamol , Thayumanavan S 
Published: December 2006

AbstractThis review discusses recent advances in protein sensing using fluorescent polyelectrolytes that are mainly water‐soluble conjugated polymers. A quencher‐labeled substrate or fluorophore‐labeled substrate is generally used as a probe. In the presence of an enzyme, the linker between substrate and quencher/fluorophore is cleaved and fluorescence of the polymer is either ‘turned on’ or ‘turned off’. Fluorescence behavior of these conjugated polymers is highly sensitive to conformation of the polymeric chains. Since upon binding with proteins the conformation is perturbed and fluorescence is affected, these polyelectrolytes have been used to study conformational changes in proteins. The conformation‐dependent fluorescence is also a limitation for these sensors in some cases and non‐conjugated polyelectrolytes have been shown to provide an alternative. Copyright © 2006 Society of Chemical Industry
ABA triblock copolymers with a ring‐opening metathesis polymerization/macromolecular chain‐transfer agent approach
Authors: Switek Karen A. , Chang Kwanho , Bates Frank S. , Hillmyer Marc A. 
Published: December 2006

AbstractBlock copolymers containing polystyrene and polycyclooctene were synthesized with a ring‐opening metathesis polymerization/chain‐transfer approach. Polystyrene, containing appropriately placed olefins, was prepared by anionic polymerization and served as a macromolecular chain‐transfer agent for the ring‐opening metathesis polymerization of cyclooctene. These unsaturated polymers were subsequently converted to the corresponding saturated triblock copolymers with a simple heterogeneous catalytic hydrogenation step. The molecular and morphological characterization of the block copolymers was consistent with the absence of significant branching in the central polycyclooctene and polyethylene blocks [high melting temperatures (114–127 °C) and levels of crystallinity (17–42%)]. A dramatic improvement in both the long‐range order and the mechanical properties of a microphase‐separated, symmetric polystyrene–polycyclooctene–polystyrene block copolymer sample was observed after fractionation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 361–373, 2007
Influence of a reversible addition–fragmentation chain transfer agent in the dispersion polymerization of styrene
Authors: Saikia Prakash J. , Lee Jung Min , Lee Byung H. , Choe Soonja 
Published: December 2006

AbstractDispersion polymerization was applied to the controlled/living free‐radical polymerization of styrene with a reversible addition–fragmentation chain transfer (RAFT) polymerization agent in the presence of poly(N‐vinylpyrrolidone) and 2,2′‐azobisisobutyronitrile in an ethanol medium. The effects of the polymerization temperature and the postaddition of RAFT on the polymerization kinetics, molecular weight, polydispersity index (PDI), particle size, and particle size distribution were investigated. The polymerization was strongly dependent on both the temperature and postaddition of RAFT, and typical living behavior was observed when a low PDI was obtained with a linearly increased molecular weight. The rate of polymerization, molecular weight, and PDI, as well as the final particle size, decreased with an increased amount of the RAFT agent in comparison with those of traditional dispersion polymerization. Thus, the results suggest that the RAFT agent plays an important role in the dispersion polymerization of styrene, not only reducing the PDI from 3.34 to 1.28 but also producing monodisperse polystyrene microspheres. This appears to be the first instance in which a living character has been demonstrated in a RAFT‐mediated dispersion polymerization of styrene while the colloidal stability is maintained in comparison with conventional dispersion polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 348–360, 2007
Poly(L‐lysine) and clay nanocomposite with desired matrix secondary structure: Effects of polypeptide molecular weight
Authors: Hule Rohan A. , Pochan Darrin J. 
Published: December 2006

AbstractNanocomposites (NC) were formed using cationic poly(L‐lysine) (PLL), a semicrystalline polypeptide, that was reinforced by sodium montmorillonite (MMT) clay via solution intercalation technique. By varying solution conditions such as pH, temperature, and polypeptide concentration in the presence of clay platelets, the secondary structure of PLL was controllably altered into α‐helical, β‐sheet, and random coil. The high molecular weight polypeptide shows a strong propensity to fold into the β‐sheet structure when cast as films, irrespective of the initial secondary structure in solution. Nanocomposite local morphology confirms intercalated MMT platelets with PLL over a wide range of compositions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 239–252, 2007.
Exploring zipping and assembly as a protein folding principle
Authors: Voelz Vincent A. , Dill Ken A. 
Published: December 2006

AbstractIt has been proposed that proteins fold by a process called “Zipping and Assembly” (Z&A). Zipping refers to the growth of local substructures within the chain, and assembly refers to the coming together of already‐formed pieces. Our interest here is in whether Z&A is a general method that can fold most of sequence space, to global minima, efficiently. Using the HP model, we can address this question by enumerating full conformation and sequence spaces. We find that Z&A reaches the global energy minimum native states, even though it searches only a very small fraction of conformational space, for most sequences in the full sequence space. We find that Z&A, a mechanism‐based search, is more efficient in our tests than the replica exchange search method. Folding efficiency is increased for chains having: (a) small loop‐closure steps, consistent with observations by Plaxco et al. 1998;277;985–994 that folding rates correlate with contact order, (b) neither too few nor too many nucleation sites per chain, and (c) assembly steps that do not occur too early in the folding process. We find that the efficiency increases with chain length, although our range of chain lengths is limited. We believe these insights may be useful for developing faster protein conformational search algorithms. Proteins 2007. © 2006 Wiley‐Liss, Inc.
Effects of acid exposure on the conformation, stability, and aggregation of monoclonal antibodies
Authors: Ejima Daisuke , Tsumoto Kouhei , Fukada Harumi , Yumioka Ryosuke , Nagase Kazuo , Arakawa Tsutomu , Philo John S. 
Published: December 2006

AbstractExposure of antibodies to low pH is often unavoidable for purification and viral clearance. The conformation and stability of two humanized monoclonal antibodies (hIgG4‐A and ‐B) directed against different antigens and a mouse monoclonal antibody (mIgG1) in 0.1M citrate at acidic pH were studied using circular dichroism (CD), differential scanning calorimetry (DSC), and sedimentation velocity. Near‐ and far‐UV CD spectra showed that exposure of these antibodies to pH 2.7–3.9 induced only limited conformational changes, although the changes were greater at the lower pH. However, the acid conformation is far from unfolded or so‐called molten globule structure. Incubation of hIgG4‐A at pH 2.7 and 3.5 at 4°C over the course of 24 h caused little change in the near‐UV CD spectra, indicating that the acid conformation is stable. Sedimentation velocity showed that the hIgG4‐A is largely monomeric at pH 2.7 and 3.5 as well as at pH 6.0. No time‐dependent changes in sedimentation profile occurred upon incubation at these low pHs, consistent with the conformational stability observed by CD. The sedimentation coefficient of the monomer at pH 2.7 or 3.5 again suggested that no gross conformational changes occur at these pHs. DSC analysis of the antibodies showed thermal unfolding at pH 2.7–3.9 as well as at pH 6.0, but with decreased melting temperatures at the lower pH. These results are consistent with the view that the antibodies undergo limited conformational change, and that incubation at 4°C at low pH results in no time‐dependent conformational changes. Titration of hIgG4‐A from pH 3.5 to 6.0 resulted in recovery of native monomeric proteins whose CD and DSC profiles resembled those of the original sample. However, titration from pH 2.7 resulted in lower recovery of monomeric antibody, indicating that the greater conformational changes observed at this pH cannot be fully reversed to the native structure by a simple pH titration. Proteins 2007. © 2006 Wiley‐Liss, Inc.
Protein dynamics from X‐ray crystallography: Anisotropic, global motion in diffuse scattering patterns
Authors: Meinhold Lars , Smith Jeremy C. 
Published: December 2006

AbstractUnderstanding X‐ray crystallographic diffuse scattering is likely to improve our comprehension of equilibrium collective protein dynamics. Here, using molecular dynamics (MD) simulation, a detailed analysis is performed of the origins of diffuse scattering in crystalline Staphylococcal nuclease, for which the complete diffuse scattering pattern has been determined experimentally. The hydrogen‐atom contribution and the scattering range over which the scattering can be considered to be a sum of solvent and protein scattering are determined. Two models of correlated protein motion are investigated by calculating the model‐derived diffuse scattering and comparing with the scattering calculated directly from MD trajectories. In one model, previously used in diffuse scattering interpretation, the atomic displacement correlations decay isotropically with increasing separation. Model correlation lengths are obtained by refining the model scattering against the simulation‐derived scattering pattern, and are found to be significantly different from those correlation lengths derived directly from the MD trajectories. Furthermore, the convergence between the model‐derived and MD‐derived scattering is poor. The second model, in which the displacement correlations are calculated from the principal components of the MD trajectories, is capable of fully reproducing the MD‐derived diffuse scattering if the ≈50% lowest‐frequency modes are included. However, a small number (≈10) of lowest‐frequency and largest‐amplitude modes dominates the diffuse scattering and thus the correlated protein motions. A detailed analysis of the principal components is performed. In particular, the effective free energy profile associated with each principle mode is analyzed and the eigenfrequency and damping coefficient computed using a model of Brownian dynamics. Those collective modes with effective frequencies below ≈0.5 THz, including those that determine the diffuse scattering, are overdamped. Proteins 2007. © 2006 Wiley‐Liss, Inc.