bluuebunny/crossref_metadata_2025 huggingface dataset:
Modification of polyolefins with silicone copolymers. I. Processing behavior and surface characterization of PP and HDPE blended with silicone copolymers
Authors: Yilgor Iskender , Yilgor Emel , Suzer Sefik
Published: August 2002

Permanent surface modification of polypropylene and high‐density polyethylene was obtained by blending with small (0.1 to 5.0% by weight) amounts of silicone copolymers. A triblock polycaprolactone‐b‐polydimethylsiloxane copolymer and a multiblock polydimethylsiloxane–urea copolymer were used as modifiers. Blends were prepared in a twin‐screw extruder. Influences of the type and amount of the additive on the processing behavior and surface and bulk properties of the resulting systems were investigated. During processing, the additives also acted as very efficient processing aids, increasing the extruder output dramatically, up to 200%. Surface characterization by water‐contact angle measurements and X‐ray photoelectron spectroscopy clearly showed the formation of silicone‐rich surfaces even with very small amounts of additives, such as 0.1% by weight. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1625–1634, 2002
Effect of hydrogen‐bond‐breaking reagent (urea) on the dimensional stability of rat tail tendon (RTT) collagen fiber
Authors: Usha R. , Ramasami T.
Published: August 2002

Influence of hydrogen‐bond‐breaking reagents such as urea on shrinkage temperature, isometric tension, swelling behavior, tensile strength, and percentage extension of native rat tail tendon (RTT) were examined. The swelling behavior was observed with polarizing optical microscopy and scanning electron microscopy. The results show that the lyotropic swelling increased the width of the fiber and was associated with the action of urea on the collagen fiber. Hydration properties led to significant variations in the swelling phenomenon. Lyotropic swelling produced opaque, limp, and flaccid fibers that did not change appreciably in length. The melting behavior and the swollen fascicles were clearly seen in scanning electron micrographs of 3 and 6M urea‐treated RTT. The reduction in the dimensional stability of native RTT collagen fiber on treatment with urea demonstrated the role of secondary structure in the dimensional stabilization of collagen. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 975–982, 2002; DOI 10.1002/app.10262
Synthesis, characterization, and in vitro release of ibuprofen from poly(MMA‐HEMA) copolymeric core–shell hydrogel microspheres for biomedical applications
Authors: Sivakumar M. , Rao K. Panduranga
Published: August 2002

This article describes the development of a new crosslinked poly(methyl methacrylate‐2‐hydroxyethyl methacrylate) copolymeric core–shell hydrogel microsphere incorporated with ibuprofen for potential applications in bone implants. Initially poly(methyl methacrylate) (PMMA) core microspheres were prepared by free‐radical initiation technique. On these core microspheres, 2‐hydroxyethyl methacrylate (HEMA) was polymerized by swelling PMMA microspheres with the HEMA monomer by using ascorbic acid and ammonium persulfate. Crosslinking monomers such as ethylene glycol dimethacrylate (EGDMA) has also been included along with HEMA for polymerization. By this technique, it was possible to obtain core–shell‐type microspheres. The core is a hard PMMA microsphere having a hydrophilic poly(HEMA) shell coat on it. These microspheres are highly hydrophilic as compared to PMMA microspheres. The size of the hydrogel microspheres almost doubled when swollen in benzyl alcohol. These microspheres were characterized by various techniques such as optical microscopy, scanning electron microscopy, Fourier‐transformed infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The particle size of both microspheres was analyzed by using Malvern Master Sizer/E particle size analyzer. The in vitro release of ibuprofen from both microspheres showed near zero‐order patterns. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3045–3054, 2002; DOI 10.1002/app.10310
Microencapsulation of water‐soluble herbicide by interfacial reaction. II. Release properties of microcapsules
Authors: Yeom C. K. , Kim Y. H. , Lee J. M.
Published: August 2002

Chitosan microcapsules containing the water‐soluble herbicide 3‐hydroxy‐5‐methylisoxazole were fabricated at different fabrication conditions by a new microencapsulation process established in the previous work. Selecting chitosan as a capsule wall could be justified because chitosan not only has a biodegradable characteristic but also enhances the fertility of soil after degradation in the ground. The microcapsules prepared at an agitation speed of higher than 12,000 rpm were smaller than 5 μm in diameter, and the release of the active material from the capsules into pure water was sustained for 80–160 h, depending on the agitation speed used in microencapsulation. The effects of fabrication variables were discussed on the capsule size and release properties of the fabricated microcapsules. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1025–1034, 2002; DOI 10.1002/app.10383
Preparation of chemically crosslinked gels with maleate‐denatured poly(vinyl alcohol) and its application to drug release
Authors: Horiike Satoshi , Matsuzawa Shuji , Yamaura Kazuo
Published: August 2002

Maleate‐denatured poly(vinyl alcohol) (M‐PVA) was crosslinked with heating. The mechanism of crosslinking was studied with several procedures: titration, Fourier transform infrared, and solubility. The carboxyl groups of M‐PVA consisted of carboxylates and a few free carboxyl groups. The crosslink was the ester linkage between hydroxyl and carboxyl groups. Several kinds of M‐PVA tablets were prepared under different conditions: pressures of 200–600 kgf/cm2 and grain sizes of 75 (pass) to 250 μm (on). The swelling behavior of these chemically crosslinked tablets was studied in a buffer solution of pH 7.4, mainly at 37°C. Moreover, the effect of temperature from 5 to 50°C and the effect of repeated swell–dry cycles on the behavior of the tablets in a buffer solution [106 μm (on), 200 kgf/cm2] were studied. The release of p‐acetamidophenol from those tablets in the pH 7.4 buffer solution was studied. The different release patterns were due to the differences in the swelling behavior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1178–1184, 2002; DOI 10.1002/app.10411
Influence of branching on the thermal behavior of poly(butylene isophthalate)
Authors: Finelli Lara , Lotti Nadia , Munari Andrea
Published: August 2002

The thermal behavior of linear and randomly branched poly(butylene isophthalate) samples was investigated by thermogravimetric analysis and differential scanning calorimetry. As to the thermal stability, it was found to be good and similar for all the samples. The thermal analysis carried out using DSC technique showed that the melting temperature of the polymers decreased with increasing branching unit content, although the glass‐transition temperature was practically not affected by ramifications. The multiple endotherms typical of linear PBI were also observed in branched samples and were found to be influenced both by temperature and degree of branching. By applying the Hoffman‐Weeks' method, the equilibrium melting temperatures of the polymers were obtained. The presence of a crystal‐amorphous interphase was evidenced only for the branched samples and the interphase amount was found to increase as the branching unit content was increased. Isothermal melt crystallization kinetics was analyzed according to Avrami's treatment. The introduction of branching points was found to decrease the overall crystallization rate of poly(butylene isophthalate). Values of Avrami's exponent n close to 3 were obtained for all the samples, in agreement with a crystallization process originating from predetermined nuclei and characterized by three dimensional spherulitic growth. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2001–2010, 2002; DOI 10.1002/app.10517
Novel synthesis of diketocarboxymethyl‐celluose as bipolymer precursors
Authors: Khairou K. S. , Hassan R. M. , Shaker A. M.
Published: August 2002

2,3‐Diketocarboxymethylcellulose was prepared by the oxidation of carboxymethylcellulose (CMC) with potassium permanganate in alkaline solutions (pH ≥ 12) with a yield of 98.1%. IR spectroscopy and microanalysis have elucidated the chemical structure of the synthesized macromolecule (CMCK). A tentative reaction mechanism for oxidation is suggested. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1019–1023, 2002
Highly efficient nucleating additive for isotactic polypropylene studied by differential scanning calorimetry
Authors: Marco C. , Gómez M. A. , Ellis G. , Arribas J. M.
Published: August 2002

The influence of an organic phosphate derivative in the crystallization of the monoclinic phase of isotactic polypropylene was studied by differential scanning calorimetry. To analyze the nucleation activity of the additive, the self‐nucleation process of the pure polymer was also studied by thermal techniques. A large increase in crystallization temperatures was obtained even for the lowest concentration of the additive, and its nucleating efficiency is the highest observed for α‐nucleating agents in isotactic polypropylene. The nucleating agent was also observed to increase the stability of the crystals formed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1669–1679, 2002; DOI 10.1002/app.10546
Effects of the crosslinking agent and diluents on bead properties of styrene–divinylbenzene copolymers
Authors: Kangwansupamonkon W. , Damronglerd S. , Kiatkamjornwong S.
Published: August 2002

Styrene–divinylbenzene copolymer beads were synthesized by radical suspension polymerization. Effects of the divinylbenzene concentration and composition of the toluene/heptane diluent were studied regarding the polymer bead formation, surface morphology, solvent swelling ratio, and glass transition temperature. The crosslinking density and diluent composition were responsible for solvent swelling. Interaction between the polymer and the diluents is attributed to phase separation, which controls the formation of a network‐type or pore‐type polymer, or a combination. For an optimum bead swelling in toluene, a combined morphology of more flexible polymer networks and a small amount of pores is essential for the desired absorption–desorption behavior. This article also combines several current findings with work presented elsewhere to explain the bead formation phenomenon. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 654–669, 2002
Dicyanate ester–polyetherimide semi‐interpenetrating polymer networks. II. Effects of morphology on the fracture toughness and mechanical properties
Authors: Harismendy I. , Del Río M. , Marieta C. , Gavalda J. , Mondragon I.
Published: August 2002

A high temperature thermosetting bisphenol‐A dicyanate (BADCy) was modified with polyetherimide (PEI) at various compositions. The effects of the morphology of the blends on the fracture toughness and mechanical properties were investigated. For this purpose, fracture, flexural, and compression tests were carried out. The fracture surfaces of the broken specimens were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The morphology was controlled by changing the curing conditions and PEI content. A good correlation between fracture properties and microstructural features of the mixtures has been observed. The phase‐inverted morphologies showed the highest fracture toughness, which was further increased by increasing the cure temperature. The mechanical properties of the matrix (modulus, yield strength) were not affected by the addition of the thermoplastic. Fracture energy values show similar trends for the different mechanical tests performed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2759–2767, 2001
UV photopolymerization behavior of dimethacrylate oligomers with camphorquinone/amine initiator system
Authors: Yu Q. , Nauman S. , Santerre J. P. , Zhu S.
Published: August 2002

Ultraviolet (UV)‐initiated polymerization of dimethacrylate oligomers with camphorquinone (CQ) and a tertiary amine as a radical photoinitiator system was studied using differential scanning calorimetry. Polymerization behavior of two curing systems, one glass‐forming and the other elastomer‐forming, were compared, based on the rate of polymerization and the double bond conversion. The radical termination in the glass‐forming system (E‐bis‐A DMA‐1) became diffusion controlled immediately upon exposure to UV radiation, with the reaction rate quickly reaching its maximum. The elastomer‐forming system (E‐bis‐A DMA‐2) polymerized at a much lower rate than E‐bis‐A DMA‐1 because of its lower methacrylate group content. The two systems introduced a different temperature dependence on the rate of polymerization. Increasing the temperature reduced the viscosity and enhanced chain segmental mobility. This delayed the autoacceleration in the glass‐forming system. Polymerization rates for both the curing systems increased with initiator concentration, but the dependence on CQ was only characterized by an exponential factor of <0.5. Presumably, this was due to primary radical recombination. The vinyl group conversion and gel fraction of E‐bis‐A DMA‐1 increased with the increase in CQ concentration and/or curing temperature, while the extent of reaction for E‐bis‐A DMA‐2 was relatively insensitive to the latter two factors. A large number of radicals were trapped inside the network of E‐bis‐A DMA‐1 after photocuring and they decayed slowly. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1107–1117, 2001
Influence of temperature, molecular weight, and molecular weight dispersity on the surface tension of PS, PP, and PE. I. Experimental
Authors: Moreira José Carlos , Demarquette Nicole Raymonde
Published: August 2002

In this work, the influence of temperature, molecular weight (M̄n), and molecular weight dispersity (MWD) on the surface tension of polystyrene (PS) was evaluated using the pendant drop method. The influence of temperature on the surface tension of isotatic polypropylene (i‐PP) and of linear low‐density polyethylene (LLDPE) was also studied here. It was shown that surface tension decreases linearly with increasing temperature for all the polymers studied. The temperature coefficient −dγ/dT (where γ is the surface tension, and T, the temperature) was shown to decrease with increasing molecular weight and to increase with increasing MWD. The surface tension of PS increased when the molecular weight was varied from 3400 to 41,200 g/mol. When the molecular weight of PS was further increased, the surface tension was shown to level off. The surface tension was shown to decrease with increasing molecular weight distribution. Contact angles formed by drops of diiomethane and water on films of PS with different molecular weights were measured at 20°C. The surface energies of those polymers were then evaluated using the values of the different pairs of contact angles obtained here using two different models: the harmonic mean equation and the geometric mean equation. It was shown that the values of the surface energy obtained are slightly less than are the ones extrapolated from surface‐tension measurements in the rubbery state. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1907–1920, 2001
Additive diffusion coefficients in polyolefins. II. Effect of swelling and temperature on the D = f(M) correlation
Authors: Reynier Alain , Dole Patrice , Feigenbaum Alexandre
Published: August 2002

Diffusion coefficients of a large panel of molecules were experimentally measured in virgin polypropylene at 40 and 70°C and in swollen polypropylene at 40°C. The influence of mobility increase brought out by temperature or swelling are compared. The effects are more important for high molecular weight compounds. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2434–2443, 2001
Study of the mechanical properties of mica‐filled polypropylene‐based GMT composite
Authors: Zhao Ruofei , Huang Jin , Sun Bin , Dai Gance
Published: August 2002

Mica‐filled polypropylene (PP)‐based GMT (PP–mica–GMT) was prepared by a double‐belt press and its mechanical properties were tested. The effect of the mica content on the mechanical properties of PP–mica–GMT was investigated. It was found that with a lower mica content in matrix the tensile and flexural properties were improved; however, at a high mica content level, the tensile and flexural properties decreased. With respect to the impact strength, there is a maximum value at an approximate 20 wt % mica content level. These results were attributed to the influence of mica on fiber–matrix adhesion. It is most likely that low mica content enhances fiber–matrix adhesion; however, high mica content is unfavorable to fiber–matrix adhesion. Maleic anhydride‐grafted PP (MPP) was used to enhance the fiber–matrix adhesion at a higher mica loading level for PP–mica–GMT. With increasing MPP content in the matrix, the tensile properties were significantly improved, whereas the Izod impact strength decreased. In addition, with 5 wt % MPP and 40 wt % mica in the PP matrix formulation, the effect of the mica particle size and glass fiber content on the mechanical properties of PP–mica–GMT was investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2719–2728, 2001
Laboratory instruction in histology at the University at Buffalo: Recent replacement of microscope exercises with computer applications
Authors: Cotter John R.
Published: August 2002

Histology is a morphologic science in which the structure of the cells, tissues, and organs of the body are examined with a microscope. In the laboratory courses in histology at the School of Medicine of the University at Buffalo, histologic specimens had been used since the late 19th century to teach the principles of cell, tissue, and organ structure. Students also had to learn how to analyze or “read” slides with a microscope. Learning histology in this way, i.e., by direct examination of actual specimens, is time consuming and viewed by some as unnecessary. As a result of recent curricular reform at the School of Medicine that reduced contact time in histology, half of all laboratory exercises that would have been performed with a microscope were performed instead with interactive computer applications. By replacing some microscope exercises with more efficient computer applications, the histology course accommodated curricular change by both reducing contact time and continuing to offer valuable microscope laboratories for most of the organ systems of the body. To provide a basis for comparing traditional microscope exercises with computer‐assisted instruction in histology, the nature of the laboratory experience between 1846 and 1998 is briefly reviewed. The instructional strategy behind the use of computers is presented, along with the nature of the computer applications and the means by which the computer applications were incorporated into the school's laboratory course in histology. Anat Rec (New Anat) 265:212–221, 2001. © 2001 Wiley‐Liss, Inc.
It's ethical, but is it legal? Teaching ethics and law in the medical school curriculum
Authors: Olick Robert S.
Published: August 2002

While Western medical ethics has ancient roots in the teachings of Hippocrates, its standing in the undergraduate medical curriculum is a distinctly modern development. Today, all of the 127 accredited U.S. medical schools offer formal biomedical ethics instruction, and nearly all offer instruction in the related discipline of health law. This article describes how biomedical ethics and health law are taught at the University of Iowa College of Medicine, one of 12 medical schools that offers separate required courses in both ethics and law. Often ethics and law overlap; often, to act ethically is to act legally. But medical students and practicing physicians also regularly confront dilemmas that pose the question, “It's ethical, but is it legal?” This article discusses the goals, methods, and core themes of teaching issues at the intersection of medicine, ethics, and law, and how the approach to this instruction is designed to offer students a tool kit to begin to deal effectively with these complex issues in professional life. Anat Rec (New Anat) 265:5–9, 2001. © 2001 Wiley‐Liss, Inc.
Hormonal activation of phosphorylase in cockroach fat body trophocytes: A correlation with trans‐membrane calcium flux
Authors: Steele J. E. , Ireland R.
Published: August 2002

This study is an investigation of the temporal relationship between transmembrane Ca2+ fluxes, and glycogen phosphorylase activation in dispersed trophocytes from the fat body of the cockroach, Periplaneta americana. Phosphorylase is maximally activated within 5 min after treating the trophocytes with either of the hypertrehalosemic hormones, Pea‐HTH‐I and Pea‐HTH‐II. Activation caused by Pea‐HTH‐II is sustained for a longer period than that produced by Pea‐HTH‐I. Chelation of extracellular Ca2+ with EGTA blocks the activation of phosphorylase by HTH. Similarly, chelation of intracellular Ca2+ with Quin 2 greatly diminishes the phosphorylase activating effect of both HTHs. The data support the view that an increase in the intracellular Ca2+ concentration is required for the activation of phosphorylase and that extracellular Ca2+ is an essential, although not necessarily sole, source of Ca2+ for this purpose. Using 45Ca2+ to trace the movement of Ca2+ following a challenge with either Pea‐HTH‐I or ‐II, it was shown that 45Ca2+influx nearly doubled during the first 30 s. At this time, the trophocytes begin to expel Ca2+ at a rate higher than that of untreated cells and this state persists for approximately 4 min. The Ca2+ fluxes are consistent with its postulated role in the activation of phosphorylase. Arch. Insect Biochem. Physiol. 42:233–244, 1999. © 1999 Wiley‐Liss, Inc.
Increased ribonucleotide reductase activity in hydroxyurea‐resistant mosquito cells
Authors: Gerenday Anna , Shih Karen M. , Herman Carter C. , Fallon Ann M.
Published: August 2002

Hydroxyurea‐resistant Aedes albopictus mosquito cells were selected by incremental exposure of unmutagenized cells to hydroxyurea concentrations ranging from 0.1 to 8 mM. Clonal populations that had become 40‐fold more resistant to hydroxyurea than wild‐type cells varied in morphology, and their growth rate decreased to a ˜45 h doubling time, relative to an 18 h doubling time in unselected cells. At this level of resistance, the cells remained diploid, with a modal chromosome number of 6. When labelled with 35S[methionine/cysteine], clone HU1062, which grew in the presence of 8 mM hydroxyurea, overproduced a labeled protein with the approximate size of the 45,000 dalton M2 subunit of ribonucleotide reductase. Consistent with this observation, ribonucleotide reductase activity in HU‐1062 cells was approximately 10‐fold higher than in wild‐type control cells. This is the first example of an hydroxyurea‐resistant insect cell line. Arch. Insect Biochem. Physiol. 34:31–41, 1997. © 1997 Wiley‐Liss, Inc.
Expression of neuroparsin cDNA in insect cells using baculovirus vectors
Authors: Girardie J. , Chaabihi H. , Fournier B. , Lagueux M. , Girardie A.
Published: August 2002

The cDNA encoding neuroparsin A, a polytropic neurohormone of the locust, Locusta migratoria, was inserted into the genome of Autographa californica nuclear polyhedrosis virus such that transcription was under control of the p10 promoter. A polypeptide having the same charge and the same apparent molecular weight as the authentic neuroparsin A and that was reactive against neuroparsin immune serum was produced in recombinant virus‐infected lepidopteran cell lines but not in control virus‐infected cells. The baculovirus‐expressed polypeptide was purified by two steps of liquid chromatography (anion exchange and reversed phase) which were previously used to purify the natural neuroparsin. The purified baculovirus‐expressed polypeptide enhanced fluid reabsorption of everted rectum preparations, as did the natural neuroparsin. Thus, this gene expression system produced a polypeptide identical to authentic neuroparsin. Arch. Insect Biochem. Physiol. 36:11–23, 1997. © 1997 Wiley‐Liss, Inc.
Magnetic resonance imaging of normal and osteoarthritic trabecular bone structure in the human knee
Authors: Beuf Olivier , Ghosh Srinka , Newitt David C. , Link Thomas M. , Steinbach Lynne , Ries Michael , Lane Nancy , Majumdar Sharmila
Published: August 2002

Objective

To use high‐resolution magnetic resonance imaging (MRI) to evaluate the trabecular bone structure in the distal femur and the proximal tibia and its to correlate the findings with different stages of osteoarthritis (OA) of the human knee.

Methods

Axial images of the distal femur and proximal tibia were obtained at 1.5 T in patients without and with mild OA and with severe OA. The spatial resolution was 195 × 195 μm2 with a 1‐mm slice thickness. Apparent measures of trabecular bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular separation (Tb.Sp), and trabecular thickness (Tb.Th) were calculated.

Results

Significant differences existed in the trabecular bone structure of the femur and tibia. Differences in trabecular bone structure between the tibia and the femur decreased with the degree of OA. The apparent BV/TV, Tb.N, and Tb.Sp in the femoral condyles could be used to differentiate healthy patients or patients with mild OA from patients with severe OA (P < 0.05). Among individuals, the structural variation of the lateral and medial femoral condyle was indicative of the extent of the disease.

Conclusion

High‐resolution MRI of the knee joint can provide a noninvasive assessment of trabecular bone structure. Trabecular bone structure, determined by high‐resolution MRI, shows significant variation in patients with varying degrees of OA. The impact of OA on trabecular bone is different in the tibia than in the femur, and this difference depends on the extent of the disease.
Disposition and receptor‐site binding of 125I‐EGF after topical administration to skin wounds
Authors: Prats P.A. , Duconge J. , Valenzuela C. , Berlanga J. , Edrosa C.R. , Fernández‐Sánchez E.
Published: August 2002

The rhEGF topical delivery systems have been hindered by a number of shortcomings which have led to the search of new development strategies. In this study we report the evaluation of cumulative profiles of 10, 5 and 1 µg/ml solutions of 125I‐rhEGF, in a rat full‐thickness skin wound model, as well as the drug‐induced modulation in the expression of the EGF receptor after lesion. The tissue‐associated radioactivity, expressed as the percentage of the dose administered per grams of tissue (%D/g), peaks at 2 h after administration of all doses. 125I‐rhEGF degraded species were detected chromatographically, but no diffusion of the peptide to the surrounding skin was documented. Despite the dose, the EGF receptor expression was increased within 2 h after wounding, followed by a slow decline up to 12 h below baseline. Twelve hours after punch, differences were evident between all treated groups and control. These results demonstrate that 125I‐rhEGF saline solutions are rapidly cleared from application sites, probably by protease‐driven cleavage and receptor‐mediated endocytosis. Finally, we must be aware that the results herein discussed should be taken into account during the drug delivery system design in order to guarantee the necessary steady‐state rhEGF levels upon wound healing process. Copyright © 2002 John Wiley & Sons, Ltd.
50 Hz magnetic fields of varying flux intensity affect cell shape changes in invertebrate immunocytes: The role of potassium ion channels
Authors: Ottaviani Enzo , Malagoli Davide , Ferrari Alex , Tagliazucchi Davide , Conte Angela , Gobba Fabriziomaria
Published: August 2002

The effect induced by exposure to 50 Hz magnetic fields (MFs) in immunocytes from the mussel Mytilus galloprovincialis is evaluated. The whole animal was exposed for 15 and 30 min to MF intensities ranging from 200 to 1,000 μT. The changes in the cellular shape of immunocytes, expressed as shape factor (SF), were studied at different times after addition of the chemotacting substance N‐formyl‐Meth‐Leu‐Phe (fMLP). Results show that MFs provoke differing delays in fMLP‐induced cellular shape changes: 200 μT are ineffective, while levels from 300 μT upwards cause a significant increase in immunocyte SF values compared to controls. Reactivation of the cells is possible up to an intensity of 600 μT. The use of PCO 400, an opener of ATP‐sensitive K+ channels, shows that potassium channels are involved in the effect of MFs on M. galloprovincialis immunocytes. Bioelectromagnetics 23:292–297, 2002. © 2002 Wiley‐Liss, Inc.
Mammalian DNA single‐strand break repair: an X‐ra(y)ted affair
Authors: Caldecott Keith W.
Published: August 2002

The genetic stability of living cells is continuously threatened by the presence of endogenous reactive oxygen species and other genotoxic molecules. Of particular threat are the thousands of DNA single‐strand breaks that arise in each cell, each day, both directly from disintegration of damaged sugars and indirectly from the excision repair of damaged bases. If un‐repaired, single‐strand breaks can be converted into double‐strand breaks during DNA replication, potentially resulting in chromosomal rearrangement and genetic deletion. Consequently, cells have adopted multiple pathways to ensure the rapid and efficient removal of single‐strand breaks. A general feature of these pathways appears to be the extensive employment of protein–protein interactions to stimulate both the individual component steps and the overall repair reaction. Our current understanding of DNA single‐strand break repair is discussed, and testable models for the architectural coordination of this important process are presented. BioEssays 23:447–455, 2001. © 2001 John Wiley & Sons, Inc.
Divergence pattern of animal gene families and relationship with the Cambrian explosion
Authors: Miyata Takashi , Suga Hiroshi
Published: August 2002

There are many gene families that are specific to multicellular animals. These have either diverged from ancestral genes that are shared with fungi and/or plants or evolved from an ancestral gene unique to animals. The evolution of gene families involved in cell–cell communication and developmental control has been studied to establish whether the number of member genes increased dramatically immediately prior to or in concert with the Cambrian explosion. A molecular phylogeny‐based analysis of several animal‐specific gene families has revealed that gene diversification by duplication occurred during two active periods interrupted by a long intervening quiescent period. Intriguingly, the Cambrian explosion is situated in the silent period, indicating that there is no direct link between the first burst of gene diversification and the Cambrian explosion itself. The importance of gene recruitment as a possible molecular mechanism for morphological diversity, and its possible role for the Cambrian explosion, are discussed. BioEssays 23:1018–1027, 2001. © 2001 John Wiley & Sons, Inc.
Genetics of the Drosophila flight muscle myofibril: a window into the biology of complex systems
Authors: Vigoreaux Jim O.
Published: August 2002

This essay reviews the long tradition of experimental genetics of the Drosophila indirect flight muscles (IFM). It discusses how genetics can operate in tandem with multidisciplinary approaches to provide a description, in molecular terms, of the functional properties of the muscle myofibril. In particular, studies at the interface of genetics and proteomics address protein function at the cellular scale and offer an outstanding platform with which to elucidate how the myofibril works. Two generalizations can be enunciated from the studies reviewed. First, the study of mutant IFM proteomes provides insight into how proteins are functionally organized in the myofibril. Second, IFM mutants can give rise to structural and contractile defects that are unrelated, a reflection of the dual function that myofibrillar proteins play as fundamental components of the sarcomeric framework and biochemical “parts” of the contractile “engine”. BioEssays 23:1047–1063, 2001. © 2001 John Wiley & Sons, Inc.
Viability, strength, and fragmentation of Saccharopolyspora erythraea in submerged fermentation
Authors: Stocks S. M. , Thomas C. R.
Published: August 2002

Two fermentations of the commercially impor‐tant erythromycin‐producing filamentous bacterium Saccharopolyspora erythraea were conducted in defined media. One was glucose‐limited and the other nitrate‐limited. The viability of the hyphae was determined using the fluorescent stain BacLightTM (Molecular Probes, Eugene, OR). Also, the force required to strain hyphae to breakage was determined using micromanipulation and a sensitive force transducer. In both fermentations, fragmentation coincided with the appearance of regions in the mycelia with permeabilised membranes (considered nonviable). Under glucose‐limitation, hyphal breaking force rose to 1,050 ± 130 nN at the end of the growth phase and fell to an undetectable value as a result of glucose exhaustion. Under nitrate‐limitation, hyphal breaking force fell from 900 ± 160 nN during the growth phase to 550 ± 40 nN in the stationary phase. In both cases image analysis showed that the dimensions of mycelia were of the same order, suggesting that the major factor influencing fragmentation was the appearance of nonviable regions (assumed to be weak). The location in which nonviable regions first appear within hyphae could not be determined because of their appearance coinciding with fragmentation. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 702–709, 2001.
Expression of functional mammalian P450 2E1 in hairy root cultures
Authors: Banerjee Suchitra , Shang Tanya Q. , Wilson Angela M. , Moore Allison L. , Strand Stuart E. , Gordon Milton P. , Lafferty Doty Sharon
Published: August 2002

P450 2E1 is an important mammalian liver enzyme known to metabolize a wide range of compounds including several common environmental pollutants. The medicinal plant,Atropa belladonna, was transformed withAgrobacterium rhizogenescontaining a binary vector with rabbit P450 2E1 in either the sense or antisense orientation. The resulting “hairy roots” were isolated and grown in liquid medium. Production of P450 2E1 protein was verified in the roots containing the 2E1 gene in the sense orientation. Transgenic and control root cultures were dosed with the environmental pollutant, trichloroethylene (TCE), and were analyzed for the TCE metabolites, chloral and trichloroethanol. The root cultures expressing the mammalian P450 2E1 had increased levels of the metabolites compared to the levels in the control roots. This method represents a quick way to screen transformants for expression of foreign genes before regeneration of whole plants, and also as a possible source of foreign protein for purification. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 462–466, 2002; DOI 10.1002/bit.10151
Toluene biofiltration by the fungus Scedosporium apiospermum TB1
Authors: García‐Peña E. I. , Hernández S. , Favela‐Torres E. , Auria R. , Revah S.
Published: August 2002

The performance of biofilters inoculated with the fungus Scedosporium apiospermum was evaluated. This fungus was isolated from a biofilter which operated with toluene for more than 6 months. The experiments were performed in a 2.9 L reactor packed with vermiculite or with vermiculite‐granular activated carbon as packing material. The initial moisture content of the support and the inlet concentration of toluene were 70% and 6 g/m3, respectively. As the pressure drop increased from 5–40 mm H2O a strong initial growth was observed. Stable operation was maintained for 20 days with a moisture content of 55% and a biomass of 33 mg biomass/g dry support. These conditions were achieved with intermittent addition of culture medium, which permitted a stable elimination capacity (EC) of 100 g/m3reactorh without clogging. Pressure drop across the bed and CO2 production were related to toluene elimination. Measurement of toluene, at different levels of the biofilter, showed that the system attained higher local EC (200 g/m3rh) at the reactor outlet. These conditions were related to local humidity conditions. When the mineral medium was added periodically before the EC decreases, EC of approximately 258 g/m3rh were maintained with removal efficiencies of 98%. Under these conditions the average moisture content was 60% and 41 mg biomass/g dry support was produced. No sporulation was observed. Evaluation of bacterial content and activities showed that the toluene elimination was only due to S. apiospermum catabolism. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 61–69, 2001.
Process for degradation of nitrobenzene: Combining electron beam irradiation with biotransformation
Authors: Zhao Jian‐Shen , Ward Owen P. , Lubicki Piotr , Cross James D. , Huck Peter
Published: August 2002

Electron beam irradiations of aqueous solutions containing 15–30 mg/L of nitrobenzene at 60 kGy dose removed 78% of the contaminant. Three mononitrophenols were detected as by‐products of electron beam treatment of nitrobenzene. A mixed culture enriched on a mixture of 2‐, 3‐, and 4‐nitrophenol degraded both the residual nitrobenzene and the nitrophenol products. Percentage removal of nitrobenzene increased with increasing electron beam dose. This observation led to the conceptual design of a two‐stage electron beam microbial process for degradation of nitrobenzene. Three groups of pure isolates were characterized from the mixed culture based on their abilities to grow on cor‐ responding nitrophenol substrates: Group A, 2NP−3NP−4NP+; Group B, 2NP+3NP+4NP−; and Group C, 2NP−3NP+4NP−. Bacteria that grew on 3‐NP transformed nitrobenzene into ammonia in the electron beam‐treated nitrobenzene samples. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 73: 306–312, 2001.
Fluorescent detection of cyanobacterial DNA using bacterial magnetic particles on a MAG‐microarray
Authors: Matsunaga Tadashi , Nakayama Hideki , Okochi Mina , Takeyama Haruko
Published: August 2002

Bacterial magnetic particles (BMPs) were used for the identification of cyanobacterial DNA. Genus‐specific oligonucleotide probes for the detection of Anabaena spp., Microcystis spp., Nostoc spp., Oscillatoria spp., and Synechococcus spp. were designed from the variable region of the cyanobacterial 16S rDNA of 148 strains. These oligonucleotide probes were immobilized on BMPs via streptavidin‐biotin conjugation and employed for magnetic‐capture hybridization against digoxigenin‐labeled cyanobacterial 16S rDNA. Bacterial magnetic particles were magnetically concentrated, spotted in 100‐μm‐size microwell on MAG‐microarray, and the fluorescent detection was performed. This work details the development of an automated technique for the magnetic isolation, the concentration of hybridized DNA, and the detection of specific target DNA on MAG‐microarray. The entire process of hybridization and detection was automatically performed using a magnetic‐separation robot and all five cyanobacterial genera were successfully discriminated. © 2001 John Wiley & Sons, Inc., Biotechnol Bioeng 73: 400–405, 2001.
Effects of charged water‐soluble polymers on the stability and activity of yeast alcohol dehydrogenase and subtilisin Carlsberg
Authors: Foreman Trudi M. , Khalil Mona , Meier Paul , Brainard James R. , Vanderberg Laura A. , Sauer Nancy N.
Published: August 2002

Remarkable increases in enzyme catalytic stability resulting from addition of charged water‐soluble polymers have recently been reported, suggesting that use of these polymers may be an attractive general strategy for enzyme stabilization. To test the proposed hypothesis that coulombic forces between water‐soluble polymers and enzymes are primarily responsible for enzyme stabilization, we examined the catalytic stability and activity of two enzymes in the presence of polymers differing in net charge. All polymers tested increased enzyme lifetimes, regardless of their net charge, suggesting that stabilization of these enzymes by water‐soluble polymers is not solely dependent on simple electrostatic interactions between the polymers and enzymes. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 241–246, 2001.
High‐performance liquid chromatographic profiling of fluorescent labelled N‐glycans on glycoproteins
Authors: Yuen C.‐T. , Gee C. K. , Jones C.
Published: August 2002

Monitoring protein glycosylation is becoming increasingly important as novel recombinant glycoprotein therapeutics, such as glycoprotein hormones, cytokines and clotting factors, are introduced into clinical use. In this report, we describe an HPLC strategy and an improved and simplified pre‐column derivatization procedure to profile N‐linked glycans obtained from a variety of commercially available glycoproteins as examples. N‐Glycans were first released by peptide:N‐glycosidase F and labelled with the fluorescent label, 4‐aminobenzoic acid by reductive amination. The labelled N‐Glycans were then resolved by normal‐phase HPLC and the N‐glycan profile could be further improved by separating the N‐glycans first according to charge by anion‐exchange HPLC prior to the normal‐phase HPLC. If required, identification of the fractionated derivatized oligosaccharides can be determined by mass spectrometry. The whole profiling process is simple and can be implemented in most laboratories. Because of the high sensitivity, batch glycan‐analysis of low‐yield recombinant glycoproteins such as samples in ampoules or obtained in the early stage of production development is possible. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of 24,25‐dihydroxyvitamin D3 in human plasma using liquid chromatography‐mass spectrometry after derivatization with a Cookson‐type reagent
Authors: Higashi Tatsuya , Awada Dalsuke , Shimada Kazutake
Published: August 2002

A practical LC‐MS method for determination of (24R)‐24,25‐dihydroxyvitamin D3 [24,25(OH)2D3] in human plasma has been developed using derivatization with a Cookson‐type reagent, 4‐[4‐(6‐methoxy‐2‐benzoxazolyl)phenyl]‐1,2,4‐triazoline‐3,5‐dione (MBOTAD). The derivatization with MBOTAD significantly improved the ionization efficiency of the analyte with a detection limit of 18 fmol [equivalent to 7.5 pg of 24,25(OH)2D3] per injection. The method employed protein precipitation with acetonitrile, purification with OASIS HLB cartridge and silica gel column, derivatization with MBOTAD and atmospheric pressure chemical ionization MS detection. The mass spectrometer was operated in the positive‐ion mode of mass chromatography and [26,26,26,27,27,27‐2H6]‐24,25(OH)2D3 was used as an internal standard. The intra‐ and inter‐assay coefficients of variation were below 3.4 and 2.5%, respectively, and the analytical recovery of 24,25(OH)2D3 was quantitative. Assay linearity was obtained in the range of 0.05–1.2 ng per tube and the limit of quantitation was 0.23 ng/mL for a 0.3 mL plasma aliquot. The developed method was applied to plasma samples obtained from volunteers and gave satisfactory results. Copyright © 2001 John Wiley & Sons, Ltd.

Abbreviations used:

CPBA

Competitive protein binding assay

DBP

vitamin D binding protein

DMEQ7AD

4‐[2‐(6,7‐dimethoxy‐4‐methyl‐3‐oxo‐3,4‐dihydroxyvitaminyl)ethyl]‐1,2,4‐triazoline‐3,5‐dione

MBOTAD

4‐[4‐(6‐methoxy‐2‐benzoxazolyl)phenyl]‐1,2,4‐triazoline‐3,5‐dione

1,25(OH)2D3

1α,25‐dihydroxyvitamin D3

24,25(OH)2D3

(24R)‐24,25‐dihydroxyvitamin D3

25,26(OH)2D3

25,26‐dihydroxyvitamin D3

PTAD

4‐phenyl‐1,2,4‐triazoline‐3,5‐dione
Use of fluorescently labelled deoxyribonuclease I to spatially measure G‐actin levels in migrating and non‐migrating cells
Authors: Cramer L. P. , Briggs L. J. , Dawe H. R.
Published: August 2002

Lamellipodium protrusion is linked to actin filament disassembly in migrating fibroblasts [Cramer, 1999: Curr. Biol. 9:1095–1105]. To further study this relationship, we have identified a method to specifically and sensitively detect G‐actin in distinct spatial locations in motile cells using deoxyribonuclease I (DNase I). Although DNase I can bind both G‐ and F‐actin in vitro [Mannherz et al., 1980: Eur. J. Biochem. 95:377–385], when cells were fixed in formaldehyde and permeabilized in detergent, fluorescently‐labelled DNase I specifically stained G‐actin and not F‐actin. 92–98% of actin molecules were stably retained in cells during fixation and permeabilization. Further, increasing or decreasing cellular G‐actin concentration by treating live cells with latrunculin‐A or jasplakinolide, respectively, caused a respective increase and decrease in DNase I cell‐staining intensity as expected. These changes in DNase I fluorescence intensity accurately reflected increases and decreases in cellular G‐actin concentration independently measured in lysates prepared from drug‐treated live cells (regression coefficient = 0.98). This shows that DNase I cell‐staining is very sensitive using this method. Applying this method, we found that the ratio of G‐/F‐actin is lower in both the lamellipodium and in a broad band immediately behind the lamellipodium in migrating compared to non‐migrating fibroblasts. Thus, we predict that protrusion of the lamellipodium in migrating fibroblasts requires tight coupling to filament disassembly at least in part because G‐actin is relatively limited within and behind the lamellipodium. This is the first report to directly demonstrate high sensitivity of cell‐staining for any G‐actin probe and this, together with the ready commercial accessibility of fluorescently‐labelled DNase I, make it a simple, convenient, and sensitive tool for cell‐staining of G‐actin. Cell Motil. Cytoskeleton 51:27–38, 2002. © 2002 Wiley‐Liss, Inc.
Multiple antibodies to titin immunoreact with AHNAK and localize to the mitotic spindle machinery
Authors: Wernyj Roman P. , Ewing Charles M. , Isaacs William B.
Published: August 2002

Recently, the large filamentous striated‐muscle protein titin has been observed in non‐muscle cells, and, in one instance, has been proposed to have a nuclear function as a chromosomal component contributing to structure and elasticity. In this study, we sought to further characterize the presumptive nuclear isoform of titin. Immunofluorescence microscopy with multiple titin‐specific monoclonal antibodies shows localization to the nucleus in interphase cells and to the spindle machinery in mitotic cells in all cell types examined; localization to condensed chromosomes is not observed. An abundant 700‐kDa phosphoprotein is the predominant species immunoprecipitated with these antibodies. Sequencing of peptide fragments of the immunopurified protein reveals identity to AHNAK, a nuclear phosphoprotein, an identification that was confirmed by Western blot analysis with antibodies to AHNAK and peptide fragmentation patterns. Sequence comparison suggests similarities between the repetitive heptad ϕ±ϕP±ϕ± motif in AHNAK and the PEVK region of titin, potentially explaining the cross‐reactivity observed between AHNAK antibodies and titin antibodies. Interestingly, although some AHNAK antibodies stain interphase nuclei, no evidence of mitotic spindle localization is seen, suggesting that the identity of the protein at the latter location is more closely related to titin than AHNAK. This concept is further supported by observations that cell lines not expressing AHNAK have similar antititin antibody localization to the mitotic spindle. We conclude that (1) multiple titin antibodies, particularly those recognizing the PEVK region, cross‐react with AHNAK, and (2) the mitotic spindle staining observed with antititin antibodies is most likely due to the association of titin or a titin‐like molecule with this structure. Cell Motil. Cytoskeleton 50:101–113, 2001. © 2001 Wiley‐Liss, Inc.