bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of mechanical forces on the patterning of the avian feather‐bearing skin: A biomechanical analysis of the integumentary musculature in birds
Authors: Homberger Dominique G. , de Silva Kumudini N.
Published: August 2003

The integumentary musculature of birds consists of three distinct components. The smooth musculature comprises feather and apterial muscles, which form a continuous musculo‐elastic layer within the dermis. The feather muscles, which consistently include at least erectors and depressors, interconnect contour feathers within pterylae (i.e., feather tracts) along gridlines that are oriented diagonally to the longitudinal and transverse axes of the body. The apterial muscles interconnect pterylae by attaching to the contour feathers along their peripheries. The striated musculature is composed of individual subcutaneous muscles, most of which attach to contour feathers along the caudal periphery of pterylae A new integrative functional analysis of the integumentary musculature proposes how apterial muscles stabilize the pterylae and modulate the tension of the musculo‐elastic layer, and how subcutaneous muscles provide the initial stimulus for erector muscles being able to ruffle the contour feathers within pterylae. It also shows how the arrangement of the contour feathers and integumentary muscles reflects the stresses and strains that act on the avian skin. These mechanical forces are in effect not only in the adult, especially during flight, but may also be active during feather morphogenesis. The avian integument with its complex structural organization may, therefore, represent an excellent model for analyzing the nature of interactions between the environment and genetic material. The predictions of our model are testable, and our study demonstrates the relevance of integrated analyses of complex organs as mechanically coherent systems for evolutionary and developmental biology.J. Exp. Zool. (Mol. Dev. Evol.) 298B:123–139, 2003.© 2003 Wiley‐Liss, Inc.
Transcriptional activation of the metallothionein I gene by electric pulses in vivo: basis for the development of a new gene switch system
Authors: Rubenstrunk Anne , Orsini Cécile , Mahfoudi Abderrahim , Scherman Daniel
Published: August 2003

Background

In vivo gene transfer to skeletal muscle is a promising strategy for the treatment of muscular disorders and for the systemic delivery of therapeutic proteins. Nevertheless, for a safe and effective protein production, the spatial and temporal control of gene expression is critical. The existing regulating systems rely on the use of an exogenously regulatory protein and/or an inducer drug whose pharmacological properties are of major concerns for therapeutic applications in humans. Therefore, new strategies based on endogenous regulatable elements have been explored.

Methods

Gene expression profiles of skeletal muscle submitted or not to electrical pulses and harvested at different times were compared using the Affymetrix GeneChip technology. The endogenous metallothionein promoter was studied by Northern blot and semiquantitative and quantitative RT‐PCR. The inducibility of the metallothionein I promoter placed in a plasmid exogenous context was studied using the murine SEAP reporter gene.

Results

The expression of metallothionein I mRNA is significantly increased 6 h after electric pulses delivery. This induction is transient. Identical MT‐I expression level is observed after several sequential series of pulses delivery. We demonstrated as well that the MT‐II promoter was sensitive to electric pulses delivery. Moreover, the metallothionein I promoter, placed in a plasmid context in front of a reporter gene, was also activated by the application of transient electric field.

Conclusions

We identified a promoter highly inducible by the controlled electric stimuli applied for electrotransfer experiments. The use of the metallothionein promoter is promising for the time‐control by physical stimuli of the expression of a therapeutic gene. Copyright © 2003 John Wiley & Sons, Ltd.
Adenovirus‐mediated gene transfer to adult mouse cardiomyocytes is selectively influenced by culture medium
Authors: Li Zhenbo , Sharma Ram V. , Duan Dongsheng , Davisson Robin L.
Published: August 2003

Background

As development of cardiac gene therapies progresses, virally mediated genetic manipulations in cultured cardiomyocytes has become an important experimental approach. While adenovirus (Ad)‐mediated gene transfer to neonatal and adult rat cardiomyocytes is well established, viral transduction of cultured adult mouse cardiomyocytes (AMCM) has been more difficult. This study was designed to test the hypothesis that culture medium is a critical determinant of efficient gene transfer in AMCM.

Methods

AMCM from 8‐week‐old C57BL/6 mice were cultured in either minimum essential medium (MEM) or medium M199 and then infected with an Ad β‐galactosidase and transduction efficiency was quantified by cytochemistry and β‐galactosidase activity assay. Coxsackie‐adenovirus receptor (CAR) levels and Ad binding were evaluated by immunocytochemistry in M199‐ vs. MEM‐cultured AMCM.

Results

Our results demonstrated dramatic differences in efficiency of Ad‐mediated gene transfer in AMCM cultured in MEM (90 ± 8%) vs. M199 (5 ± 1.2%). This difference was specific to AMCM, and was not observed in a number of other cells including neonatal rat cardiomyocytes. The enhanced transduction in MEM was associated with increased levels of CAR and Ad binding in AMCM.

Conclusions

Culture medium has a profound effect on the efficiency of Ad‐mediated gene transfer in AMCM, perhaps via differential effects on CAR expression. These findings have important implications for increasing numbers of studies that employ viral gene transfer in adult cardiomyocytes derived from mouse models of cardiac diseases. Copyright © 2003 John Wiley & Sons, Ltd.
Establishment of embryonic neuroepithelial cell lines exhibiting an epiplastic expression pattern of region specific markers
Authors: Nardelli Jeannette , Catala Martin , Charnay Patrick
Published: August 2003

Neuroepithelial b2T cells were derived from the hindbrain and the spinal cord of mouse transgenic embryos, which expressed SV40 T antigen under the control of a Hoxb2 enhancer. Strikingly, b2T cell lines of either origin exhibit a very similar gene expression pattern, including markers of the hindbrain and the spinal cord, such as Hox genes, but not of more anterior cephalic regions. In addition, the broad expression pattern of b2T cells, probably linked to culture conditions, appeared to be appropriately modulated when the cells were reimplanted at different longitudinal levels into chick host embryos, suggesting that these cells are responsive to exogenous signalling mechanisms. Further support for these allegations was obtained by culturing b2T cells in defined medium and by assessing the expression of Krox20, an odd‐numbered rhombomere marker, which appeared to be modulated by a complex interplay between FGF, retinoic acid (RA), and noggin. With respect to these as yet unique properties, b2T cells constitute an original alternative tool to in vivo models for the analysis of molecular pathways involved in the patterning of the neural tube. © 2003 Wiley‐Liss, Inc.
Antiatherogenic properties of lipid minor constituents from seed oils
Authors: Karantonis Haralabos C , Zabetakis Ioannis , Nomikos Tzortzis , Demopoulos Constantinos A
Published: August 2003

A number of lines of evidence suggest that seed oils exhibit a protective effect against atherogenesis. Most of the protective compounds are still unidentified. In this study, polar lipids of seed oil samples from sesame, corn and sunflower were successively fractionated by high‐performance liquid chromatography. Each isolated lipid compound was tested in vitro for its ability to inhibit platelet‐activating factor (PAF) and thrombin‐induced washed rabbit platelet aggregation or to cause platelet aggregation. A significant number of lipids that exerted the above biological activities were detected. The most biologically active compounds were subjected to biological, chemical and spectroscopic analyses, and their structural data are presented. These results give a different explanation for the antiatherogenic action that seed oils exert. Given that PAF plays a pivotal role in atherogenesis, the fact that these oils contain PAF antagonists suggests their high nutritional value. Copyright © 2003 Society of Chemical Industry
Nutritive value of chicken and potato mixtures for infant and preschool children feeding
Authors: Sotelo Angela , Perez Lourdes
Published: August 2003

Two chicken/potato protein mixtures (50:50 and 60:40) were prepared for use in formulas of high nutritive value and low cost for the diet of undernourished children and those with lactose intolerance. The proximate analysis and amino acid content of the raw materials and mixtures were determined and the chemical score (CS) was calculated. The proximate analysis and amino acid content of a commercial soybean formula were used as reference. The protein quality of the mixtures was evaluated by protein efficiency ratio (PER) and digestibility measurements. The protein content of cooked chicken and potato on a dry basis was 889 and 70 g kg−1 respectively and the carbohydrate content of potato was 762 g kg−1. Tryptophan was the limiting amino acid in chicken for infants according to the 1985 FAO pattern (CS = 76), but not for preschool children. Valine was limiting in potato for both infants and preschool children (CS = 56 and 88 respectively). Tryptophan was limiting in both 50:50 and 60:40 mixtures for infants; also the PER was higher in the 60:40 mixture and not significantly different from the control (casein), but both were different from the 50:50 mixture. Since both chicken and potato are available even for low‐income people, a formula prepared in the 60:40 ratio is of potential benefit for infants or preschool children who have lactose intolerance, mainly in developing countries. Copyright © 2003 Society of Chemical Industry
Analysing the freshness of intact rice grains by colour determination of peroxidase activity
Authors: Chen TF , Chen CL
Published: August 2003

Freshness is an important palatability characteristic of rice grains. However, this characteristic deteriorates rapidly during dry storage. In the present study we have developed an indirect method to examine the freshness of rice grains harvested in different crop seasons or stored under conditions known to accelerate deterioration. Bulk samples of intact brown rice grains were soaked in dianisidine solution containing guaiacol and H2O2, and the optical absorbance of the incubation solution was determined colorimetrically. Alternatively, intact brown rice grains were incubated in a similar solution in the wells of a 96‐well microplate, with one grain per well, and the optical absorbance of the incubation solution was measured by a microplate reader. The results indicated that cultivar, storage duration and temperature significantly affected the activities of grain peroxidase. Marked differences in the development of purple colour in the incubation solutions and in vitro peroxidase activity were also found among the brown rice grains sampled in different seasons. The changes in colour of the incubation solutions measured by either of the above methods paralleled the changes in grain activity of peroxidase assayed using an in vitro method. The proposed method can differentiate brown rice grains harvested in different seasons. Moreover, this method, if combined with suitable statistical clustering procedures, can detect the blending status of fresh/old brown grains in a sample. The advantages of this test method using A385 over the conventional enzyme activity assay are the rapidity and simplicity with which A385 can estimate the in vitro determination of peroxidase activity of tested rice grains. Copyright © 2003 Society of Chemical Industry
Effects of roasting on ruminal nutrient degradability of sunflower seed
Authors: Sarrazin P , Mustafa AF , Chouinard PY , Raghavan GSV , Sotocinal SA
Published: August 2003

A study was conducted to determine the effects of roasting sunflower seed using heated particulate medium (heated salt at 250 °C, 60 s contact of salt and sunflower seed and 120 s holding time) on crude protein (CP) fractions, ruminal dry matter (DM) and CP degradabilities, and ruminal disappearance of amino and fatty acids. Two ruminally fistulated cows were used in a randomised complete block design. Roasting of sunflower seed decreased (P < 0.05) soluble protein and increased (P < 0.05) neutral detergent‐insoluble protein with little effect on acid detergent‐insoluble protein. Results of the in situ nylon bag study showed that roasting decreased (P < 0.05) ruminal degradability of DM and CP and increased (P < 0.05) ruminal undegraded CP of sunflower seed. Roasting increased (P < 0.05) intestinal digestibility of ruminal undegraded protein. Ruminal disappearance of all amino acids (following 12 h of incubation) was greater (P < 0.05) for raw than for roasted sunflower seed. Similar results were also observed for ruminal disappearance of fatty acids. It was concluded that roasting of sunflower seed using heated salt decreased ruminal nutrient degradabilities and thus increased the concentrations of amino acids and polyunsaturated fatty acids available for digestion in the small intestine. Copyright © 2003 Society of Chemical Industry
Endoscopic laser imaging of tissue perfusion: New instrumentation and technique
Authors: Forrester K.R. , Stewart C. , Leonard C. , Tulip J. , Bray R.C.
Published: August 2003

Background and Objectives

New instrumentation, based on a previously established laser speckle perfusion imaging (LSI) technique is evaluated for its ability to capture and generate blood flow images during endoscopic surgery.

Study Design/Materials and Methods

Investigations are detailed in an in‐vitro blood flow model simulating physiological properties of vascularized tissue, and in‐vivo in rabbit joint capsule tissue.

Results

In‐vitro measurements showed a linear response of the instrument to blood flow in the range of 0–800 μl/minute, where data points were significantly correlated with an r2 value of 0.96. In‐vivo measurements showed a 58.7% decrease to the medial collateral ligament during occlusion of the femoral artery.

Conclusions

Blood flow images demonstrate that the endoscopic LSI technique is capable of measuring relative tissue blood flow changes at high resolutions and rapid response times and incorporates well with endoscopic surgeries. Lasers Surg. Med. 33:151–157, 2003. © 2003 Wiley‐Liss, Inc.
Photodestruction of human dental plaque bacteria: Enhancement of the photodynamic effect by photomechanical waves in an oral biofilm model
Authors: Soukos Nikolaos S. , Mulholland Stephen E. , Socransky Sigmund S. , Doukas Apostolos G.
Published: August 2003

Background and Objectives

Periodontal disease results from the accumulation of subgingival bacterial biofilms on tooth surfaces. There is reduced susceptibility of these biofilms to antimicrobials for reasons that are not known. The goals of this study were to investigate the photodynamic effects of a conjugate between the photosensitizer (PS) chlorine6 (ce6) and a poly‐l‐lysine (pL) with five lysine residues on human dental plaque bacteria as well as on biofilms of the oral species Actinomyces naeslundii after their exposure to photomechanical waves (PW) generated by a laser in the presence of the conjugate.

Study Design/Materials and Methods

Subgingival plaque samples from 12 patients with chronic destructive periodontitis were divided in 3 groups that were incubated for 5 minutes with 5 μM ce6 equivalent from the pL–ce6 conjugate in the presence of fresh medium (group I), PBS (group II), and 80% PBS/20% ethylenediaminetetra‐acetic acid (EDTA) (group III) and were exposed to red light. Also, biofilms of A. naeslundii (formed on bovine enamel surfaces) were exposed to PW in the presence of 5 μM ce6 equivalent from the pL–ce6 conjugate and were then irradiated with red light. The penetration depth of the conjugate was measured by confocal scanning laser microscopy (CSLM). In both cases, after illumination serial dilutions were prepared and aliquots were spread over the surfaces of blood agar plates. Survival fractions were calculated by counting bacterial colonies.

Results

The PS/light combination achieved almost 90% killing of human dental plaque species. In biofilms of A. naeslundii, CSLM revealed that PW were sufficient to induce a 50% increase in the penetration depth of the pL–ce6 conjugate into the biofilm. This enabled its destruction (99% killing) after photodynamic therapy (PDT).

Conclusions

PW‐assisted photodestruction of dental plaque may be a potentially powerful tool for treatment of chronic destructive periodontal disease. Lasers Surg. Med. 33:161–168, 2003. © 2003 Wiley‐Liss, Inc.
Fiber spinning behavior of a 3‐hydroxybutyrate/3‐hydroxyhexanoate copolymer
Authors: Bond Eric Bryan
Published: August 2003

The fiber spinning behavior of a poly(3‐hydroxyalkanoate) (PHA) copolymer resin containing 11.3 mol% hexanoate copolymer (H11) was studied to determine its usefulness in fiber based applications, such as nonwovens. Monocomponent fibers were spun initially, but it was found they would not solidify in the spinline. Bicomponent (sheath/core) fibers were melt spun using a H11 core and a polylactic acid (PLA), as well as a polyethylene succinate (PES) sheath. The spinning results showed that H11 levels up to 30wt% could be incorporated with stable spinning. The incorporation of H11 was found to be limited due to the slow crystallization kinetics of the H11 in the spinline. The neat and bicomoponent fibers were found to have tensile strengths similar to polypropylene. The PES based fiber compositions were found to have elongation‐at‐break values similar to PP. Neat H11 copolymer fibers were found to be readily biodegradable at 25°C under aerobic conditions.
Thermosetting of wheat protein based bioplastics: modeling of mechanism and material properties
Authors: Domenek Sandra , Morel Marie‐Hélène , Redl Andreas , Guilbert Stéphane
Published: August 2003

Structural investigation of gluten‐glycerol blends subjected to heat‐treatment was carried out by size‐exclusion high performance liquid chromatography (SEC) and stress‐strain tests. SEC is a valuable tool to investigate the size distribution of gluten protein chains, while the molecular weight between network junctions (Me) can be estimated from the elastic plateau modulus. Wheat gluten aggregation upon thermosetting seems to proceed through direct covalent cross‐linking between glutenin oligomers and the gluten macropolymer. The time course of the reaction, which showed a slow‐down of the reaction rate with time, was described by a simple mechanistic model. The deceleration of the reaction rate was presumably due to the development of a three‐dimensional protein network, which decreased the accessibility of reactive groups. The network formation could be evidenced separately by the decrease of Me during the heat‐treatment.
The performance of degradable polymer bags
Authors: Davis Georgina , Bulson Hugh , Harrison David , Billett Eric
Published: August 2003

The use of degradable polymers for the collection and composting of organic wastes is explored within this paper. With reference to one trial where the performance of a ‘degradable’ polyethylene based sack for the kerbside collection of organic wastes was investigated. Areas for consideration were the impacts of the degradable polymer on the composting process and the quality of the finished product. This trial also included a comparative study of two different types of ‘degradable’ polymer sacks currently on the European market (polyethylene and starch). A number of quantitative tests were conducted on the different polymers to assess the mechanisms of degradation and how this affected their suitability for the treatment of organic wastes. Provisional results have indicated that the polyethylene (PE) sacks are not degrading as anticipated within open windrow conditions, adversely affecting both the composting process and the quality of the finished compost product. Whilst the degradable starch based sacks appear to actively degrade within open windrow compost conditions.
Solubility islands for polymer blends – a new option to homogenize incompatible polymers?
Authors: Imre Attila R.
Published: August 2003

Experimental results of liquid‐liquid phase equilibrium in a polydisperse blend of two polyalkylsiloxane are presented here. The UCST has an unusual pressure dependence: pressure induced miscibility at moderate pressures and pressure induced immiscibility at higher pressures, above a double critical point. The cloud point curve has two maxima in (concentration, temperature) as well as in (concentration, pressure) space. Approaching the double critical point, the high and low pressure branches of the cloud point curve merge and in a certain stage of this merging, they form a miscibility island located inside the two‐phase region. Islands of this kind can give us a new tool to mix virtually immiscible blends.
Rheo‐optical determination of the interfacial tension in a dispersed blend
Authors: Tassieri Manlio , Grizzuti Nino , Greco Francesco
Published: August 2003

In this work, we present two novel methods to determine the interfacial tension of a disperse polymer blend through rheo‐optical measurements of flow‐induced single drop distortions. A counter‐rotating shearing device with transparent plates is used to measure drop distortions. The cell geometry allows for a top view of the deforming drop, i.e., along the velocity gradient direction. Such a view is the only possible option for all currently available commercial rheo‐optical instruments. Two different quantities are monitored, namely, the drop axis along the vorticity direction, and the rotation period of the drop surface. We use drops of a polyacrilamide aqueous solution (a shear thinning liquid) immersed in a polyisobutene matrix. Experimental results are interpreted in terms of theories for Newtonian liquids, where the relevant parameter is the Capillary number. If an appropriate viscosity ratio is chosen, that accounts for the shear thinning behaviour of the drop phase, good agreement is found between measurements and theoretical predictions. As a result, a robust estimate of the blend interfacial tension, that makes use only of the information acquired from top view experiments, is obtained.
Blends of an epoxy thermosetting polymer with aromatic liquid‐crystalline polyesters
Authors: Jasinski Wojciech , Carlier Véronique , Legras Roger , Mormann Werner
Published: August 2003

A series of aromatic liquid‐crystalline polyesters with different composition have been synthesized to adjust transition temperatures and molecular weight. Miscibility of polyesters with bisphenol‐A‐diglycidyl ether (DEGBA), 4,4′‐methylene‐bis(3‐chloro‐2,6‐dimethylaniline) (MCDEA) and the influence on transition temperatures has been studied. Miscibility of binary and ternary mixtures was found over the whole range of composition depending on the temperature. Thermoset formation by curing of LC‐polyester / DEGBA / MCDEA mixtures containing different amounts of polyester resulted in reaction‐induced phase separation with polyester content from 30 to 50 wt.%. Cloud point techniques, scanning electron microscopy (SEM) and dynamic mechanical thermal analysis (DMTA) have been applied.
An investigation of sPS/epoxy blends by means of x‐ray scattering techniques
Authors: Zafeiropoulos N.E. , Schut J. , Pohlers A. , Stamm M. , Gerard J.‐F.
Published: August 2003

SPS is a fast crystallisable polymer that possesses a number of interesting properties due to its semicrystalline nature. However, one major problem is the necessity of applying high temperature for processing sPS (above 290°C), as its melting point is approximately 270°C, and its degradation threshold is at 310‐320°C A possible solution to the processing problem may be blending of the sPS with another polymer to lower the viscosity, and subsequently, the processing temperature. SPS, however, exhibits polymorphism like many other semicrystalline polymers. Due to its polymorphism it is necessary to investigate the crystallisation of sPS in sPS blends. Such an investigation is conducted in the present study for the system sPS/epoxy by means of x‐ray scattering techniques. The results from WAXS revealed that the degree of crystallinity increases by decreasing the sPS content in the sPS/DGEBA blends. Investigations by means of SAXS revealed a trend of increasing the long period by decreasing the sPS content in the blends.
In situ monitoring of reaction‐induced phase separation with modulated temperature DSC
Authors: Swier Steven , Van Mele Bruno
Published: August 2003

A linearly polymerizing and network forming epoxy‐amine system, DGEBA‐aniline and DGEBA‐MDA, respectively, will be modified with 20 wt% and 50 wt% of a high‐Tg thermoplastic poly(ether sulphone) (Tg=223°C), respectively, both showing LCST‐type demixing behavior. Reaction‐induced phase separation (RIPS) in these modified systems is studied using Modulated Temperature DSC (MTDSC) as an in situ tool. Phase separation in the linear system can be probed by vitrification of the PES‐rich phase, occurring at a higher conversion than the actual cloud point from light scattering measurements. The negative slope of the cloud point curve in a temperature‐conversion‐transformation diagram unambiguously shows the LCST‐type demixing behavior of this system, while the relation between the composition/glass transition of the PES‐rich phase and the cure temperature is responsible for the positive slope of its vitrification line. Phase separation in the network forming system appears as reactivity increases at the cloud point due to the concentration of reactive groups. Different mixture compositions alter the ratio between the rate of phase separation and the rate of reaction, greatly affecting the morphology. Information about this in situ developed structure can be obtained from the heat capacity evolutions in non‐isothermal post‐cures.
Phase separation in a poly(ether sulfone) modified epoxy‐amine system studied by temperature modulated differential scanning calorimetry and dielectric relaxation spectroscopy
Authors: Montserrat S. , Roman F. , Basany M. , Colomer P.
Published: August 2003

The phase separation induced by the curing reaction of an epoxy based on diglycidylether of bisphenol A (DGEBA) with methylene dianiline (MDA) modified with poly(ether sulfone) (PES) at a concentration of 20 wt% was studied by temperature modulated differential scanning calorimetry (TMDSC) and dielectric relaxation spectroscopy (DRS). The effect of phase separation on the curing kinetics and vitrification phenomena is analysed. The dependence of the log of the measuring frequency on the degree of conversion allows the correlation between the dipolar relaxation of each phase and the vitrification observed by TMDSC to be established.
Bulk and surface properties of blends with semifluorinated polymers and block copolymers
Authors: Pospiech Doris , Häußler Liane , Jehnichen Dieter , Kollig Wolfram , Eckstein Kathrin , Grundke Karina
Published: August 2003

The goal of the investigation presented here is the development of extremely hydrophobic materials based on polysulfone that can be applied, for instance, as fouling‐resistant membrane materials. The concept used is the addition of semifluorinated polymers to polysulfone in suitable blend compositions. The influence of molecular parameters like chain structure of the semifluorinated polymer (segmented block copolymers, random copolymers) and segment molecular weight on the state of phase separation in the bulk and its influence on the surface properties have been systematically examined. It could be shown that segmented block copolymers with semifluorinated polyester segments with intermediate segment molecular weight are more suitable in blends with polysulfone than random polysulfone copolymers having semifluorinated side chains with respect to form homogeneous thin films (coatings) with highly non‐wetting properties.
Multivariate Composition Distribution in Free‐Radical Multicomponent Polymerization, 1
Authors: Tobita Hidetaka
Published: August 2003

Statistical multicomponent polymerization is a typical example of a Markovian process for which the generating function approach can be applied. Up to the present, generating functions have been used mainly to obtain analytical solutions. However, recent advances of computer software capable of handling symbolic calculations can throw new light on the old mathematical technique. After formulating the equations representing the instantaneous composition distribution of polymers for a given chain length, r, the illustrative numerical calculations are conducted by using the symbolic calculator. For a multicomponent polymerization consisting of more than two components, the second component distribution is dependent on the composition of the first component (F1), which is represented by the conditional probability given r and F1, $Comp\left( {F_2 \left| {F_1 ,r} \right.} \right)$. It is found that $Comp\left( {F_2 \left| {F_1 ,r} \right.} \right)$ is well approximated by the Gaussian distribution with the variance following the relationship, $r\sigma _{2;1,r}^2 = A + B/r$, as in the case of the first component distribution $Comp\left( {F_1 \left| r \right.} \right)$, where A and B are the constants. With the knowledge of chain length distribution, it is now possible to conduct the full analysis of multivariate distribution of chain length and compositions for multicomponent free‐radical polymerization.

Bivariate distribution of composition F1 and F2 for chain length r = 100 in a three‐component system.

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Bivariate distribution of composition F1 and F2 for chain length r = 100 in a three‐component system.
Multivariate Composition Distribution in Free‐Radical Multicomponent Polymerization, 2
Authors: Tobita Hidetaka
Published: August 2003

A shortcut approximate method is proposed for determining the multivariate composition distribution. It is found that the multivariate normal distribution can represent the major body of composition distribution for long chains reasonably well. The covariance of the multivariate composition distribution is obtained from the generating function proposed in Part 1 of this series. The covariance vij changes with chain length r, however a simple relationship, rvij = A + B/r, is found to exist, where A and B are the constants. These constants can be determined from the vij values for rather small values of r, which reduces the required amount of calculation significantly, and the multivariate composition distribution for long chains can be estimated conveniently.

Contour plot of the bivariate composition distribution for the three‐component system with r = 100. The solid curves are the exact solution, while the dotted curve is the approximation using the multivariate normal distribution.

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Contour plot of the bivariate composition distribution for the three‐component system with r = 100. The solid curves are the exact solution, while the dotted curve is the approximation using the multivariate normal distribution.
Monte Carlo Study of Heteroarm Star Copolymers in Good and Selective Solvents
Authors: Havránková Jitka , Limpouchová Zuzana , Procházka Karel
Published: August 2003

Lattice Monte Carlo simulations of conformations of hereroarm star copolymers AnBnin selective solvents were performed using a special variant of the Siepman and Frenkel algorithm. The effects of solvent quality, the number and lengths of blocks on the collapse of the insoluble block A, segregation of the two types of blocks and the behavior of the soluble blocks B were studied mainly for “hairy” stars containing high numbers of long arms. The simulation shows that insoluble blocks collapse in strongly selective solvents and the gravity centers of soluble and insoluble blocks separate which suggests the possibility of the formation of non‐spherical structures.

Snapshots of star a in a very bad solvent (T = 3.00) for blocks A. There are two different views of the star with a total number of armsf = 16 and number of segmentsN = 300.

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Snapshots of star a in a very bad solvent (T = 3.00) for blocks A. There are two different views of the star with a total number of armsf = 16 and number of segmentsN = 300.
Simulations of Electric Field Induced Lamellar Alignment in Block Copolymers in the Presence of Selective Electrodes
Authors: Kyrylyuk A. V. , Sevink G. J. A. , Zvelindovsky A. V. , Fraaije J. G. E. M.
Published: August 2003

Computer simulations have been performed for electric field induced parallel‐perpendicular lamellar phase transition in the presence of electrodes. The simulations are based on the dynamic density functional theory. Here we provide the extension of earlier work in two dimensions (2D) to three dimensions (3D). The result is a vivid picture of the transitions through defect creation and collision.

Observed change in lamellar alignment with applied electric field.

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Observed change in lamellar alignment with applied electric field.
“Volume‐Preserving” Conformational Rheological Models for Multi‐Component Miscible Polymer Blends Using the GENERIC Formalism
Authors: Eslami Hassan , Ramazani Ahmad , Khonakdar Hossein Ali
Published: August 2003

A family of conformational rheological models for multi‐component miscible polymer blends is developed using a modified form of the Poisson bracket formulation. Two conformation tensors called c1 and c2 are introduced to show the orientation of the first and the second components of a blend, respectively. The mobility tensor and the energy function for each blend component are expressed in terms of these conformation tensors. The interaction effects are also included by energy expressions. The predictions of this family of “volume‐preserving” models are illustrated for a Hookean‐type energy function and several expressions of the modified mobility tensors. The results are illustrated for material functions in transient (start‐up and relaxation) and steady shear flows. The predictions are compared with experimental data taken from the literature for a miscible polymer blend. Study of the model sensitivity to its parameter shows that model predictions can cover a wide range of rheological behavior generally observed for multi‐component miscible polymer blends in steady and transient shear flows.

Experimental data and model predictions for steady shear viscosity for HDPE/LDPE blends.

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Experimental data and model predictions for steady shear viscosity for HDPE/LDPE blends.
A Conditional Monte Carlo Method to Determine the Architectures of Metallocene Catalyzed Polyethylene
Authors: Hoefsloot Huub C. J. , Iedema Piet D.
Published: August 2003

Two polymer molecules of the same length (n) and the same number of branch points (N) can have different properties, since they may possess distinct architectures. In this paper we present a conditional Monte Carlo algorithm for the virtual synthesis of metallocene‐catalyzed polyethylene (PE) in a continuous stirred tank reactor (CSTR). The condition for the Monte Carlo method consists of a fixed chain length distribution (CLD) and a degree of branching distribution (DBD). These distributions are calculated with a Galerkin finite element method. The synthesis method is a recursive algorithm that subsequently creates insertions of sub‐structures containing numbers of branch points according to a certain probability density function. This provides an adjacency matrix describing the connectivity between the branch points, while separately a vector containing the length of segments between branch points and terminal segments is generated. Characterization of the architectures proceeds by rheological features, seniorities and priorities, and molecular properties like the radius of gyration. Comparing the radii of gyration of metallocene polyethylene and low density PE (ldPE) shows the former to possess a more comb‐like structure on average. This is confirmed by the rheological characterization. The found bivariate seniority/priority distribution agrees well to the results of an analytical study of the same chemical system.

Constituting elements of the algorithm.

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Constituting elements of the algorithm.
Interfacial Properties of Asymmetric Polymer Mixtures
Authors: Adhikari Narayan P. , Straube Ekkehard
Published: August 2003

Using a Monte‐Carlo simulation of a continuous space Rod Bead Model the interface properties of systems of flexible polymer chains with different sizes of monomers are investigated. An immiscible polymer blend in the strong segregation state is modeled by a double sandwich system of chains differing by an factor of two in the size of the beads and the interfacial tension is calculated by a virial theorem method. The simulation data are compared to self‐consistent mean field and experimental data. The results show that the simulation data agree very satisfactory with mean‐field results. The interfacial tension decreases for asymmetric systems in comparison to symmetric systems with comparable volume contents of monomers and interaction strengths due to a decrease of the effective interaction. The parameters of the investigated systems are close to the properties of PS, PMMA and PI melts. A comparison with experimental results yields a very good agreement with data for PS/PMMA and less satisfactory for PS/PI. Additionally to the interfacial tension we have studied the interfacial width, the deformation of polymer chains near the interface, distributions of chain ends, monomer densities and distributions of centers of mass of chains.

Snapshot of a typical configuration for chains with different monomer sizes and equal number of monomers per chain.

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Snapshot of a typical configuration for chains with different monomer sizes and equal number of monomers per chain.
Gelation in Multiple Link System
Authors: Suematsu Kazumi
Published: August 2003

The critical point theory is generalized to include gelation in multilink system with f functional units and J junction points. The equations derived include, as special cases, the cyclotrimerization model of J = 3, and the R–Af model of J = 2. The theory is applied to the recent observation of the cyclotrimerization of bisphenol‐A dicyanate. The theoretical prediction agrees exactly with the Stutz‐Simak observation, Dc = 0.504, and accords with the Georjon‐Galy‐Pascault observation, giving a confirmation of the physical soundness of the theory. Under the smoothness assumption, we derive post‐gelation relationships with loop formation, the result suggesting the formation of permanent sol molecules that resist being absorbed into gel phase throughout an entire reaction process.

Representation of binary branching.

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Representation of binary branching.
Involvement of the Akt/mTOR pathway on EGF‐induced cell transformation
Authors: Nomura Masaaki , He Zhiwei , Koyama Ichiko , Ma Wei‐Ya , Miyamoto Ken‐ichi , Dong Zigang
Published: August 2003

Our previous study demonstrated that phosphatidylinositol 3‐kinase (PI3K) is necessary for epidermal growth factor (EGF)–induced cell transformation in mouse epidermal JB6 cells. Akt and the mammalian target of rapamycin (mTOR) are regarded as PI3K downstream effectors. Therefore, in this study, we investigated the role of Akt and mTOR on EGF‐induced cell transformation in JB6 cells using rapamycin, a specific mTOR inhibitor, and cells expressing dominant negative mutants of Akt1 (DNM‐Akt1). We found that the treatment of cells with rapamycin inhibited EGF‐induced cell transformation but only slightly inhibited JB6 cell proliferation at 72 h. Although LY294002, a PI3K inhibitor, attenuated EGF‐induced activator protein 1 (AP‐1) activation, treatment with rapamycin did not affect AP‐1 activity. Treatment with rapamycin inhibited EGF‐induced phosphorylation and activation of ribosomal p70 S6 protein kinase (p70 S6K), an mTOR downstream target, but had no effect on phosphorylation and activation of Akt. Rapamycin also had no effect on EGF‐induced phosphorylation of extracellular signal–regulated protein kinases (ERKs). We showed that introduction of DNM‐Akt1 into JB6 mouse epidermal Cl 41 (JB6 Cl 41) cells inhibits EGF‐induced cell transformation without blocking cell proliferation. The expression of DNM‐Akt1 also suppressed EGF‐induced p70 S6K activation as well as Akt activation. These results indicated an involvement of the Akt/mTOR pathway in EGF‐induced cell transformation in JB6 cells. © 2003 Wiley‐Liss, Inc.
A new FISH assay to simultaneously detect structural and numerical chromosomal abnormalities in mouse sperm
Authors: Hill Francesca S. , Marchetti Francesco , Liechty Melissa , Bishop Jack , Hozier John , Wyrobek Andrew J.
Published: August 2003

De novo aberrations in chromosome structure represent important categories of paternally transmitted genetic damage. Unlike numerical abnormalities, the majority of de novo structural aberrations among human offspring are of paternal origin. We report the development of a three‐color fluorescence in situ hybridization (FISH) assay (CT8) to detect mouse sperm carrying structural and numerical chromosomal abnormalities. The CT8 assay uses DNA probes for the centromeric and telomeric regions of chromosome 2, and a probe for the subcentromeric region of chromosome 8. The CT8 assay was used to measure the frequencies of sperm carrying certain structural aberrations involving chromosome 2 (del2ter, dup2ter, del2cen, dup2cen), disomy 2, disomy 8, and sperm diploidy. Analysis of ∼80,000 sperm from eight B6C3F1 mice revealed an average baseline frequency of 2.5 per 10,000 sperm carrying partial duplications and deletions of chromosome 2. Extrapolated to the entire haploid genome, ∼0.4% of mouse sperm are estimated to carry structural chromosomal aberrations, which is more than fivefold lower than the spontaneous frequencies of sperm with chromosome structural aberrations in man. We validated the CT8 assay by comparing the frequencies of abnormal segregants in sperm of T(2;14) translocation carriers detected by this assay against those detected by chromosome painting cytogenetic analysis of meiosis II spermatocytes. The CT8 sperm FISH assay is a promising method for detecting structural chromosome aberrations in mouse sperm with widespread applications in genetics, physiology, and genetic toxicology. Mol. Reprod. Dev. 66: 172–180, 2003. © 2003 Wiley‐Liss, Inc.
Effects of donor oocytes and culture conditions on development of cloned mice embryos
Authors: Gao Shaorong , McGarry Michelle , Priddle Helen , Ferrier Tricia , Gasparrini Bianca , Fletcher Judy , Harkness Linda , De Sousa Paul , McWhir Jim , Wilmut Ian
Published: August 2003

Mice have been successfully cloned from somatic and embryonic stem (ES) cells using the “Honolulu method.” In the present study, different donor oocytes and different culture conditions were compared to evaluate the developmental potential of nuclear transfer embryos reconstructed with an inbred ES cell line HM‐1. Oocytes were recovered from two different F1 donors B6D2F1 (C57BL/6 × DBA/2) and B6CBAF1 (C57BL/6 × CBA). There was no effect of oocyte origin on development of cloned embryos to the morulae/blastocyst stage (B6D2F1 44.1% vs. B6CBAF1 45.0%), and the transferred embryos could develop to term. Two culture conditions were compared to show their ability to support development to the morulae/blastocyst stage of reconstructed embryos with B6D2F1 oocytes. The total cell number in the cloned blastocysts cultured in M16 with 20% oxygen was much higher than that observed in CZB with 20% oxygen. Low oxygen concentration during culture of nuclear transfer embryos in CZB medium showed no beneficial effect on pre‐implantation development, no embryos developed to term after transfer to surrogate mothers. Our results demonstrated that not only B6D2F1, but B6CBAF1 oocytes, can be used for nuclear transfer. M16 medium is superior for culture of nuclear transfer embryos and low oxygen concentration with CZB medium during culture shows no benefit on development of cloned embryos. Mol. Reprod. Dev. 66: 126–133, 2003. © 2003 Wiley‐Liss, Inc.
Role of adrenergic receptor subtypes in the control of human placental blood vessels
Authors: Resch BÉla Endre , Ducza Eszter , GÁspÁr RÓbert , Falkay George
Published: August 2003

Statements of the Problem: The use of β2‐Adrenergic Receptor (AR) agonists and the potential use of α1‐AR blockers as tocolytics raise the question of how they influence placental circulation. The receptor profile was characterized via the amounts of the mRNA of α1‐AR subtypes and β2‐ARs. The mRNAs were detected by reverse transcription‐polymerase chain reaction. Electric field stimulation (EFS) was applied to test the pharmacological reactivity of the placental vessels. Expressions of β2‐ and all subtypes of α1‐AR mRNA were demonstrated in human placental vessels, and were significantly higher in the arteries. A significant difference was not found between the veins and the arteries as concerns the amount of α1D‐AR mRNA. There was a preponderance of α1A‐ and α1B‐AR mRNA as compared to α1D‐AR mRNA both in the arteries and in the veins. β2‐AR agonists and α1‐AR antagonists antagonized the EFS‐induced contractions of the placental arteries in a dose‐dependent manner. These effects were significantly less marked on veins at all applied doses. Urapidil antagonized the EFS‐induced contractions of both the placental arterial and vein rings in a dose‐dependent manner. The β2‐, α1A‐, and α1B‐AR are the important subtypes involved in the regulation of the contractility of the human term placental vessels. The possible increase in placental blood flow mediated by these ARs can even be beneficial during pregnancy. Accordingly, the use of β2‐AR agonists and the potential use of α1‐blockers as tocolytics seem safe on the basis of in vitro examinations as concerns the placental circulation. Mol. Reprod. Dev. 66: 166‐171, 2003. © 2003 Wiley‐Liss, Inc.
Identification and quantification of differentially expressed transcripts in in vitro‐produced bovine preimplantation stage embryos
Authors: Tesfaye Dawit , Ponsuksili Siriluck , Wimmers Klaus , Gilles Markus , Schellander Karl
Published: August 2003

In this study, we used mRNA differential display reverse transcription polymerase chain reaction (DDRT‐PCR) to analyze the mRNA expression patterns in in vitro‐produced bovine 8‐cell, 16‐cell, morula, and blastocyst stage embryos and isolate differentially expressed amplicons. Moreover, we have used a fluorescence monitored real time quantitative PCR to quantify and analyze the expression patterns of the target differentially expressed transcripts through out the preimplantation stages from oocytes to blastocyst. For this, total RNA isolated from bovine 8‐cell (n = 188), 16‐cell (n = 94), morula (n = 35), and blastocyst (n = 15) were reverse transcribed and subjected to DDRT‐PCR. Target differentially expressed transcripts were quantified by real time quantitative PCR. The cDNA banding pattern analysis revealed that large number of cDNA bands were conserved at 8‐cell and blastocyst stage with a slight decrease at the morula stage. A total of 16 amplicons were cloned and sequenced. All expressed sequence tags (ESTs), except 1C19, showed sequence similarity with known genes or ESTs in GenBank. Sixty‐two percent (10/16) of cDNA bands representing differentially expressed genes originated from 8‐cell stage and the rest derived from the 16‐cell, morula, or blastocyst stage. The quantitative PCR analysis has validated the expression patterns of 75% (12/16) of our transcripts to be in agreement with the results of DDRT‐PCR. However, the quantitative PCR results of four transcripts showed a deviation from the pattern seen in DDRT‐PCR. In conclusion, we have successfully applied mRNA DDRT‐PCR to identify and isolate stage‐specific expressed genes in bovine preimplantation embryos. In addition to validating the results of DDRT‐PCR, quantitative real time PCR provides quantitative data on the expression of target genes. Mol. Reprod. Dev. 66: 105–114, 2003. © 2003 Wiley‐Liss, Inc.