bluuebunny/crossref_metadata_2025 huggingface dataset:
Amelioration of disease severity by intraarticular hylan therapy in bilateral canine osteoarthritis
Authors: Marshall K. W. , Manolopoulos V. , Mancer K. , Staples J. , Damyanovich A.
Published: February 2005

Because of its high molecular weight, the glycosaminoglycan molecule hyaluronan is responsible for the viscoelastic properties of normal synovial fluid. In osteoarthritis, the concentration and molecular weight of hyaluronan in synovial fluid is diminished; this impairs the ability of synovial fluid to effectively lubricate joints, absorb loads, and exert anti‐inflammatory effects. Using a bilateral anterior cruciateligament transection and partial neurectomy canine model of osteoarthritis, this study examined the effect of viscosupplementation with hylan G‐F 20 as a treatment for osteoarthritis, this study examined the effect of viscosupplementation with hylan G‐F 20 as a treatment for osteoarthritis. Twelve dogs underwent bilateral arthroscopic anterior cruciate‐ligament transections and partial neurectomy of the knee joints. Beginning 1 week after the operation, six dogs received three weekly 500‐μl injections of hylan G‐F 20 in one knee and a sham injection of saline solution in the contralateral knee (early‐treatment group). The remaining six animals underwent the same treatment 2 months following the procedure (late‐treatment group). All dogs were killed at 8 months, and both knees were evaluated for gross pathology, histology, and proteoglycan content. In addition, with use of 500‐MHz [1H] magnetic resonance spectroscopy, the synovial fluid from both knees was assessed for changes in metabolic profile. Differences in outcome were analyzed with pairedttests. Gross pathological and histological examination revealed significantly less severe changes of osteoarthritis in knees treated with hylan G‐F 20 2 months after surgery than in the contralateral untreated knees. Magnetic resonance spectroscopy of the specimens in this late‐treatment group showed significantly decreased glucose concentrations and significantly elevated isoleucine levels in the synovial fluid from knees treated with hylan G‐F 20 compared with the controls. Previous magnetic resonance spectroscopy had shown that glucose concentrations increase with the onset of osteoarthritis and eventually diminish in end‐stage osteoarthritis. The three injections of hylan were given after osteoarthritis was established, and the severity of the disease was ameliorated in the treated knees 6 months after treatment. This occurred although hylan G‐F 20 is almost certainly cleared from joints by lymphatics within 4 weeks of injection, suggesting that hylan therapy can retard the progression of osteoarthritis for periods of time extending beyond the intraarticular residence time of the injected molecules and that hylan injections given at relatively early stages of osteoarthritis may have a chondroprotective effect. No changes in outcome were noted in the animals that received hylan G‐F 20 immediately following surgery.
Pregnancy affects cellular activity, but not tissue mechanical properties, in the healing rabbit medial collateral ligament
Authors: Hart David A. , Reno Carol , Frank Cyril B. , Shrive Nigel G.
Published: February 2005

Recently, evidence has been accumulating that ligament and joint laxity is altered in women and rabbits during pregnancy. Furthermore, many female adolescents injure ligaments through participation in athletics and other activities. Therefore, to determine whether pregnancy has different effects on the injured and uninjured medial collateral ligament of the rabbit knee, we investigated cellular changes (mRNA levels) and alterations in tissue properties (biomechanics) accompanying pregnancy in animals with the medial collateral ligament injured during adolescence and bred for their primigravid pregnancy as young adults. Assessment of mRNA levels for matrix molecules, matrix metalloproteinases and tissue inhibitor of metalloproteinase‐1, growth factors and sex hormone receptors, inflammatory cytokines, inducible nitric oxide synthase, and cyclooxygenase‐2 by semiquantitative reverse transcription‐polymerase chain reaction revealed that pregnancy had different impacts on scar and uninjured tissue for six of 15 genes assessed. A pregnancy‐associated increase in laxity of the medial collateral ligament was observed for rabbits in the uninjured primigravida group; however, no increase was observed for injured rabbits during pregnancy. The injured ligament was already significantly more lax than the normal counterpart, and pregnancy did not lead to additional laxity or prevent the normal decline in laxity as the scar matured in nonpregnant animals. These results indicate that the impact of pregnancy on laxity and cell activity of the medial collateral ligament is dependent on whether the ligament is uninjured or injured. Pregnancy had no significant effect on structural (stiffness and failure load), material (stress at failure and Young's modulus), or viscoelastic (cyclic and static relaxation) properties of tissue from uninjured or injured medial collateral ligament. Therefore, the properties of the healing ligament were not adversely affected during pregnancy in this experimental model. However, it remains to be determined if these results with an injured medial collateral ligament can be extrapolated to the injured anterior cruciate ligament.
Compressive compared with tensile loading of medial collateral ligament scar in vitro uniquely influences mRNA levels for aggrecan, collagen type II, and collagenase
Authors: Majima Tokifumi , Marchuk Linda L. , Sciore Paul , Shrive Nigel G. , Frank Cyril B. , Hart David A.
Published: February 2005

To test the hypothesis that loading conditions can be used to engineer early ligament scar behaviors, we used an in vitro system to examine the effect that cyclic hydrostatic compression and cyclic tension applied to 6‐week rabbit medial collateral ligament scars had on mRNA levels for matrix molecules, collagenase, and the proto‐oncogenes c‐fos and c‐jun. Our specific hypothesis was that tensile stress would promote more normal mRNA expression in ligament whereas compression would lead to higher levels of mRNA for cartilage‐like molecules. Femur (injured medial collateral ligament)‐tibia complexes were subjected to a hydrostatic pressure of 1 MPa or a tensile stress of 1 MPa of 0.5 Hz for 1 minute followed by 14 minutes of rest. On the basis of a preliminary optimization experiment, this 15‐minute testing cycle was repeated for 4 hours. Semiquantitative reverse transcription‐polymerase chain reaction analysis was performed for mechanically treated medial collateral ligament scars with use of rabbit specific primer sets for types I, II, and III collagen, decorin, biglycan, fibromodulin, versican, aggrecan, collagenase, c‐fos, c‐jun, and a housekeeping gene, glyceraldehyde‐3‐phosphate dehydrogenase. Cyclic hydrostatic compression resulted in a statistically significant increase in mRNA levels of type‐II collagen (171% of nonloaded values) and aggrecan (313% of nonloaded values) but statistically significant decreases in collagenase mRNA levels (35% of nonloaded values). Cyclic tension also resulted in a statistically significant decrease in collagenase mRNA levels (66% of nonloaded values) and an increase in aggrecan mRNA levels (458% of nonloaded values) but no significant change in the mRNA levels for the other molecules. The results show that it is possible to alter mRNA levels for a subset of genes in scar tissue by supplying unique mechanical stimuli in vitro and thus that further investigation of scar engineering for potential reimplantation appears feasible.
Morphometric analysis of canine skeletal muscles following experimental callus distraction according to the ilizarov method
Authors: Fink Bernd , Neuen‐Jacob Eva , Madej Marius , Lienert Arnd , Rüther Wolfgang
Published: February 2005

Muscle fiber diameter and fiber‐type distribution were analyzed during callus distraction. The right tibia in 24 beagles was lengthened 2.5 cm by callus distraction after osteotomy and application of a ring fixator. Distraction was started at the fifth postoperative day, at a rate of two times for 0.5 mm per day. Twelve dogs that underwent limb‐lengthening and three dogs in the control group that did not undergo limb‐lengthening were killed at the end of the 25‐day distraction phase (group A). The remaining dogs (12 that underwent limb‐lengthening and three that did not) were killed after an additional consolidation period of 25 days (group B). The tibialis anterior, extensor digitorum longus, peroneus longus, and gastrocnemius muscles were removed from the right limb (which had undergone distraction) and the left control side of each animal. Crosscut cryostat sections were stained by adenosine triphosphatase at pH 4.3 and 9.4 to determine the size and distribution of types I and II fibers. Morphometric analysis of the muscle fibers was performed by a computer‐assisted two‐point technique. On the lengthened side, the muscles revealed marked atrophy affecting predominantly type‐II fiber in the dogs in group A and affecting both fiber types in dogs in group B. Fiber density increased in both groups. In addition, fiber‐type grouping indicative of reinnervation was obvious in group B. Fiber‐type distribution in the dogs in group B showed a shift toward type I in the tibialis anterior (p = 0.043) and extensor digitorum longus (p = 0.034) muscles and a shift toward type II in the gastrocnemius (p = 0.038). The data show that tension‐stress during tibial lengthening leads to atrophy of type‐II fiber, reflecting disuse of muscle fiber in the distraction period as well as neurogenic atrophy followed by the reinnervation processes. Furthermore, the data are consistent with the occurrence of histoneogenesis during limb‐lengthening resulting in an increase in fiber density.
Primary resective shortening followed by distraction osteogenesis for limb reconstruction: A comparison with simple lengthening
Authors: Meffert Rainer H. , Tis John E. , Inoue Nozomu , McCarthy Edward F. , Brug Erwin , Chao Edmund Y. S.
Published: February 2005

Resective distraction osteogenesis is a new approach to treat segmental diaphyseal bone defects by primary limb shortening and secondary distraction osteogenesis from the same site. A rabbit model was introduced to compare the bone‐regeneration characteristics of this technique with those of simple lengthening procedures. Twenty‐four skeletally mature New Zealand White rabbits were divided into two equal groups. In the test group, limbs were lengthened after a 10‐mm segmental diaphyseal bone resection and limb shortening. In the control group, a simple subperiosteal osteotomy for limb lengthening was performed without resection. New bone formation was evaluated mechanically, radiologically, histomorphometrically, and densitometrically. Bone bridging occurred in all animals. Normalized mechanical values for the newly reconstructed tibiae demonstrated similar torsional stiffness (71 ± 3.3 compared with 71 ± 8.2%; p = 0.95) and strength (64 ± 5.3 compared with 68 ± 7.3%; p = 0.66) in the two groups. The average normalized callus diameter was significantly greater in the test group than in the control group (p < 0.01). The remodeling index calculated from densitometry, however, showed a significantly less progressed stage of remodeling in the test group (p < 0.05). Histomorphometric analysis of the callus center supported this finding, showing significantly lower values for trabecular thickness (p < 0.05) and total bone volume (p < 0.01) in the test group. The results demonstrated the possibility of new bone formation after resection and monofocal shortening. This suggests a new therapeutic option to treat diaphyseal segmental bone defects.
Hyaluronan‐based polymers in the treatment of osteochondral defects
Authors: Solchaga Luis A. , Yoo Jung U. , Lundberg Magnus , Dennis James E. , Huibregtse Barbara A. , Goldberg Victor M. , Caplan Arnold I.
Published: February 2005

Articular cartilage in adults has limited ability for self‐repair. Some methods devised to augment the natural healing response stimulate some regeneration, but the repair is often incomplete and lacks durability. Hyaluronan‐based polymers were tested for their ability to enhance the natural healing response. It is hypothesized that hyaluronan‐based polymers recreate an embryonic‐like milieu where host progenitor cells can regenerate the damaged articular surface and underlying bone. Osteochondral defects were made on the femoral condyles of 4‐month‐old rabbits and were left empty or filled with hyaluronan‐based polymers. The polymers tested were ACP sponge, made of crosslinked hyaluronan, and HYAFF‐11 sponge, made of benzylated hyaluronan. The rabbits were killed 4 and 12 weeks after surgery, and the condyles were processed for histology. All 12‐week defects were scored with a 29‐point scale, and the scores were compared with a Kruskall‐Wallis analysis of variance on ranks. Untreated defects filled with bone tissue up to or beyond the tidemark, and the noncalcified surface layer varied from fibrous to hyaline‐like tissue. Four weeks after surgery, defects treated with ACP exhibited bone filling to the level of the tidemark and the surface layer was composed of hyaline‐like cartilage well integrated with the adjacent cartilage. At 12 weeks, the specimens had bone beyond the tidemark that was covered with a thin layer of hyaline cartilage. Four weeks after surgery, defects treated with HYAFF‐11 contained a rim of chondrogenic cells at the interface of the implant and the host tissue. In general, the 12‐week defects exhibited good bone fill and the surface was mainly hyaline cartilage. Treated defects received significantly higher scores than untreated defects (p < 0.05), and ACP‐treated defects scored significantly higher than HYAFF‐11‐treated defects (p < 0.05). The introduction of these hyaluronan‐based polymers into defects provides an appropriate scaffolding and favorable microen‐vironment for the reparative process. Further work is required to fully assess the long‐term outcome of defects treated with these polymers.
Healing of canine articular cartilage defects treated with microfracture, a type‐II collagen matrix, or cultured autologous chondrocytes
Authors: Breinan Howard A. , Martin Scott D. , Hsu Hu‐Ping , Spector Myron
Published: February 2005

The effects of three different treatments on the healing of articular cartilage defects were compared with use of a previously developed canine model. In the articular surface of the trochlear grooves of 12 adult mongrel dogs, two 4‐mm‐diameter defects were made to the depth of the tidemark. Four dogs were assigned to each treatment group: (a) microfracture treatment, (b) microfracture with a type‐II collagen matrix placed in the defect, and (c) type‐II matrix seeded with cultured autologous chondrocytes. After 15 weeks, the defects were studied histologically. Data quantified on histological cross sections included areal or linear percentages of specific tissue types filling the defect, integration of reparative tissue with the calcified and the adjacent cartilage, and integrity of the subchondral plate. Total defect filling (i.e., the percentage of the cross‐sectional area of the original defect filled with any type of reparative tissue) averaged 56–86%, with the greatest amount found in the dogs in the microfracture group implanted with a type‐II collagen matrix. The profiles of tissue types for the dogs in each treatment group were similar: the tissue filling the defect was predominantly fibrocartilage, with the balance being fibrous tissue. There were no significant differences in the percentages of the various tissue types among dogs in the three groups.
Differential expression of transforming growth factor‐α and macrophage colony‐stimulating factor/colony‐stimulating factor‐1R (c‐fms) by multinucleated giant cells involved in pathological bone resorption at the site of orthopaedic implants
Authors: Al‐Saffar Najat , Revell Peter A.
Published: February 2005

The immunologic response to prosthetic biomaterial particles is characterized by macrophage‐rich inflammatory infiltrate, formation of multinucleated giant cells, and aseptic loosening at the site of arthro‐plasty. We investigated the in vivo expression and tissue distribution of transforming growth factor alpha, macrophage colony‐stimulating factor, and the receptor for colony‐stimulating factor‐1 at the site of bone erosion in patients with clinically failed orthopaedic implants (n = 30). The expression was further compared with that detected in the inflamed synovial membranes from patients with rheumatoid arthritis or osteoarthritis (n = 15) and one patient with osteoclastoma (giant cell tumour of bone). Immunostaining of the tissue demonstrated positivity for transforming growth factor alpha within the inflammatory macrophage and multinucleated giant cell infiltrate in the diseased synovial membrane and the bone‐implant interface. A comparative analysis between the synovium and retrieval interface membranes (pseudosynovium) revealed a high level of expression of transforming growth factor alpha, with intense membrane staining on multinucleated giant cells in all failed arthroplasties with pseudosynovium. In addition, the frequency, antigenic phenotype, and pattern of transforming growth factor alpha expression on multinucleated giant cells in the interface were markedly similar to those observed for multinucleated giant cells in osteoclastoma. Multinucleated giant cells within the interface lacked the expression of macrophage colony‐stimulating factor and colony‐stimulating factor‐1 receptor, whereas those at the bone surfaces exhibited strong immunoreactivity. The predominant expression of transforming growth factor alpha by multinucleated giant cells in the boneimplant interface and its similarity to osteoclastoma highlight the importance of assessing transforming growth factor alpha as a possible contributor to the development of bone‐resorbing giant cells at the site of failed orthopaedic implants.
Loosening of sacral screw fixation under in vitro fatigue loading
Authors: Lu William W. , Zhu Qingan , Holmes Andrew D. , Luk K. D. K. , Zhong Shizhen , Leong C. Y.
Published: February 2005

Sacral screw fixation is frequently used for fusion of the lower lumbar spine, but sacral screws appear to offer less secure fixation than lumbar pedicle screws, and failure due to loosening under fatigue loading is common. The aim of this study was to examine in vitro the stability of medial and lateral bicortical and unicortical sacral screw fixation under a physiologically relevant fatigue‐loading pattern. Bone mineral density, screw insertion torque, and screw‐fixation stiffness were measured prior to cyclic loading between 40 and 400 N compression at 2 Hz for 20,000 cycles. The screw‐fixation stiffness was measured every 500 cycles, and the axial pullout strength of the screws was recorded following loading. All of the lateral insertions loosened under the applied loading, but some of the medial insertions remained stable. Medial insertions proved stiffer and stronger than lateral insertions, and bicortical fixations were stronger than unicortical fixations. Bone mineral density and insertion torque were correlated with screw stiffness and pullout strength, although better correlation was found for insertion torque than bone mineral density. Bone mineral density is a good preoperative indicator of sacral screw‐fixation strength, and insertion torque is a good intraoperative indicator. An insertion torque greater than 1.5 Nm is suggested as an indicative value for a stable medial unicortical insertion, whereas an insertion torque greater than 2 Nm suggests a stable medial bicortical insertion. It appears that, apart from the choice of technique (screw orientation and depth), minimizing the load on the screws during the initial part of the fusion process is also critical to maintain stability of the fused section and to obtain a solid fusion mass.
Is the circumferential tensile modulus within a human medial meniscus affected by the test sample location and cross‐sectional area?
Authors: Lechner Kate , Hull M. L. , Howell S. M.
Published: February 2005

Quantifying the material properties of the human menisci is paramount to understanding their biomechanical functions within the knee. One important intrinsic material property governing the biomechanical functions of the meniscus is the circumferential tensile modulus. The purpose of this study was to determine if the circumferential tensile modulus of the human medial meniscus depends on the location and thickness of the sample tested. The following three hypotheses were tested: (a) the circumferential location (anterior, central, and posterior) does not significantly affect the tensile modulus, (b) the radial location (inner to outer) significantly affects the tensile modulus, and (c) the thicknes (cross‐sectional area) significantly affects the tensile modulus. Test samples, whose length was oriented in parallel with the circumferential collagen fibers, were collected from different circumferential and radial locations throughout 30 human medial menisci. Samples of three different thicknesses (0.5, 1.5, and 3.0 mm) were taken from three equal groups of 10 menisci (i.e., one thickness per group). The circumferential tensile modulus was measured under quasi‐statc loading. Statistical analysis showed no significant effect of the circumferential or radial location of the sample on the circumferential tensile modulus. This indicates that an overall circumferential tensile modulus may be calculated for the human medial meniscus by averaging the values determined at the various locations. However, the thickness of the test sample had a significant effect on the measured circumferential tensile modulus: the modulus varied inversely with the thickness. Thus, moduli determined from test samples that are too small in cross‐sectional area overestimate the effective modulus of the tissue on the whole, and the cross‐sectional area of the sample must be considered when determining a representative circumferential tensile modulus for the medial meniscus in a human knee.
Tendon‐defect and muscle‐unloaded models for relating a rotator cuff tear to glenohumeral stability
Authors: Hsu Horng‐Chaung , Boardman N. Douglas , Luo Zong‐Ping , An Kai‐Nan
Published: February 2005

Rotator cuff tear and glenohumeral instability are closely related. Any tear may disturb muscle force generation due to pain inhibition. In addition, a full‐thickness tear may foster instability by removing a structural element constraining the joint. It was hypothesized that the loss of both dynamic force and static constraint with a rotator cuff tear will affect glenohumeral stability. In a tendon‐defect model, dynamic and static elements of the joint were sacrificed. In a muscle‐unloaded model, only the dynamic element was removed. The location and size of the defect were also investigated. The effect on instability of a small tendon defect was less than that of muscle unloading, implying that a patient with a small tear would have less instability than a patient with weak or nonfunctioning supraspinatus and infraspinatus muscles. On the other hand, with a larger tear the defect had a greater effect than muscle‐unloading because sectioning of the glenohumeral and coracohumeral ligaments was included in the model. Clinically, such a defect in the front is critical for anterior stability because it might insult the important anterior capsule ligamentous complex. Orthopaedic surgeons should pay attention, therefore, to the effect of possible associated lesions of static constraints based on the size and location of the tear in addition to the dynamic stabilizer.
Cyclooxygenase‐2 inhibitor SC‐236 attenuates mechanical allodynia following nerve root injury in rats
Authors: DeLeo Joyce A. , Hashizume Hiroshi , Rutkowski Maria D. , Weinstein James N.
Published: February 2005

Low back pain is a common problem, affecting approximately two‐thirds of the adult population. Of these individuals, a significant percentage will exhibit symptoms of radicular pain or sciatica. The purpose of this study was to determine the effect of one systemic (2 mg/kg) or intrathecal (0.2 mg/kg) dose of a selective cyclooxygenase‐2 inhibitor (SC‐236) in decreasing existing mechanical allodynia in a rat model of radiculopathy. Gait disturbance and mechanical allodynia (increased response to non‐noxious von Frey monofilament stimuli) were assessed daily until the rats were killed 7 days after surgery. Robust mechanical allodynia developed in the rats in all groups except for those in the sham group by day 1 after surgery. Mechanical allodynia was significantly lower in the rats that received the systemic or the intrathecal dose of SC‐236 than in those in the vehicle control group (analysis of variance followed by Bonferroni multiple comparison test, p = 0.002). The intrathecal drug route of administration produced greater attenuation in allodynia than the systemic dose, supporting a central mechanism of action of the cyclooxygenase‐2 inhibitor (p = 0.002). The hypothesis that cyclooxygenase‐2 is involved in spinal nociceptive processing after a nerve root injury was supported by this study. In addition, these data support continued basic science research to further elucidate central inflammatory processes that follow nerve root injury.
A chemist contemplates models of intermolecular collisions: A game of billiards or a demolition derby
Authors: Bauer S. H.
Published: February 2005

The kinetic molecular theory is one of the major triumphs of the physical sciences. In the following essay, we trace its current quantitative formulation, which was derived from concepts introduced during the early decades of the 19th century. Its evolution incorporated a sequence of refinements of models and of detailed mathematical analyses. Remarkably, it bridges measurable macroscopic properties and molecular parameters. However, for chemical kinetics applications it is incomplete, and its intrinsic conceptual simplifications should not be overlooked when using the theoretically derived relations. Consideration should be given to limits of applicability, and to be cognizant of features that are not fully compatible with other molecular models that are derived from diverse sources. In some measure, quantum mechanical formulations of molecular encounters bypass some of the inadequacies of the classical treatment. Herein, the designation “molecular models” refers not only to the postulated shapes, sizes, and interaction potentials of the elementary particles but also to the underlying mathematical analyses that lead to relations between observable quantities. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 191–200, 2005
Complex Adhesion Effects of Inorganic Nanofillers vs Microfillers in Polymer Composites
Authors: Kovačević V. , Leskovac M. , Lučić Blagojević S.
Published: February 2005

The adhesion parameters of fillers in composites, coefficient of wetting, interfacial free energy and work of adhesion, were calculated in order to evaluate the difference between the effects of selected microfillers vs nanofillers in polyacrylate (PA) and poly (vinyl acetate)(PVAc) matrix. The results showed that the improved fundamental adhesion, i.e. higher work of adhesion in nanocomposites resulted in the improved practical adhesion i.e. higher mechanical properties. The interfacial region was additionally modified by the controlled pre‐treatment of calcium carbonate micro‐ and nanofillers by sodium stearate that lowered the interactions with PVAc matrix. The composite morphological and mechanical properties changed accordingly. The lowered coefficient of interactions explained the pronounced composite failure at the interphase by dewetting and finally lead to the composite weakening. The conclusion about the complex relationship between the composite properties and engineering the interphase was confirmed.
Influence of the Particle Size of CaCO3 on the Adhesion of Filled EVA Materials
Authors: Martínez‐García Asunción , Sánchez‐Reche Ana , Cepeda‐Jiménez Carmen M. , Martín‐Martínez José Miguel
Published: February 2005

A surface treatment with corona discharge was used to improve the adhesion properties of ethylene vinyl acetate copolymer (EVA) containing small amounts of four CaCO3 with different particle size. The nature of the surface modifications produced by the corona discharge treatment and the adhesion to a polychloroprene adhesive were assessed. Treatment of CaCO3 filled EVA with corona discharge produced a decrease in water contact angle value, irrelevant to the different particle size of the calcium carbonates. The corona discharge treatment created C‐O and C=O moieties on the EVA surface and also increased the peel strength, more markedly as the CaCO3 particle size increased. In general, a mixed (adhesion + cohesive in the EVA) failure in the filled EVA material was produced (assessed by IR‐ATR spectroscopy and SEM micrographs of the failed surfaces), but the failure was more cohesive in the EVA containing higher particle size CaCO3. The durability of the joints was also studied.
Polypropylene‐Clay Nanocomposites: Comparison of Different Layered Silicates
Authors: Leuteritz Andreas , Pospiech Doris , Kretzschmar Bernd , Willeke Meike , Jehnichen Dieter , Jentzsch Ulrike , Grundke Karina , Janke Andreas
Published: February 2005

In former studies of the preparation of polypropylene(PP)‐clay nanocomposites, different types of layered silicates were used. However, the obtained results were not comparable due to different preparation conditions and types of silicates. The aim of this work was the investigation of the influence of different layered silicates on the properties of the resulting nanocomposites. FT‐IR‐spectra, SAXS, TEM micrographs, elemental analysis, mechanical properties and surface tension measurements were used for the comparison of the four different layered silicates under investigation.
Reprocessable and Easy Processing Silica Filled Brominated Isobutylene para Methyl Styrene (BIMS)
Authors: Wong Wai Keung
Published: February 2005

Without the use of any curatives, silica filled BIMS compounds can achieve tensile strength and bound rubber level close to conventional crosslinked elastomer compounds. This outstanding tensile performance of silica filled BIMS compounds results from the strong interaction between BIMS polymer and silica filler. Silica filled BIMS compounds can be reprocessed and still retain their high tensile strength performance. The good compatibility between BIMS and silica also leads to better filler dispersion and inhibition of filler‐filler interaction. This in turn leads to the lower processing viscosity observed. We speculate that BIMS can interact with silica via nucleophilic substitution reaction between benzylic bromide of the polymer and surface silanol group of silica.
Use of Aminosilane Coupling Agents in Cementitious Materials
Authors: Švegl Franc , Šuput‐Strupi Jerneja
Published: February 2005

The work presented in this paper has been focused on the evaluation of the influence of the addition of aminosilanes like γ‐aminopropyl‐triethoxysilane (3‐AMPS) on physical and mechanical properties of fresh and hardened polymer modified cement mortars (PMCMs), which contained also mineral fillers like fumed silica and blast furnace slag. The role of the aminosilane in cementitious system was to produce surface modification and covalent bonding among different inorganic phases of inorganic matrix (cement, aggregate, fumed silica) and strong chemical interaction between inorganic matrix and organic (polymer) phase of the mortar. The strong chemical bonding of inorganic matrix and polymer phase transformed composite mortar into cementitious material with more like monolithic structure. Mortars with the addition of aminosilanes showed improved physical‐mechanical properties like bending strength, adhesion to concrete, and lower dry‐shrinkage.
An Electroconductive Filler for Shielding Plastics
Authors: Kandasubramanian B. , Gilbert M.
Published: February 2005

A well characterised grade of mica was used to prepare nickel‐coated mica fillers by an electroless coating technique. These fillers were incorporated into polypropylene (PP) and acrylonitrile‐butadiene‐styrene (ABS) using a Haake Internal mixer and a two‐roll mill to produce conducting composites suitable for EMI shielding applications. Compounded polymers were fabricated into sheets of different thickness by compression moulding. The dependence of conductivity on sample thickness was studied and samples were tested for electrical resistivity, shielding efficiency, and thermal and mechanical properties. Reduced sample thickness during compression moulding decreased the electrical resistance of the polymer composites due to orientation and the formation of a good conducting network. Volume resistivity of PP composites was lower than for ABS composites with 50% Ni coating and equivalent filler weight fracions, showing that better conductivity could be achieved in a semi crystalline polymer than in an amorphous polymer. 0.6 weight fraction of 50 wt.% nickel coated mica in ABS showed a shielding efficiency of 16dB compared with 27.8dB in PP.
Models for the Investigation of the Structure of Vulcanizates
Authors: Magryta Jacek
Published: February 2005

For the investigation of vulcanizates structure, new models have been developed relating the modulus of vulcanizates and the volume fraction of filler. The parameters of the models are the filler distribution and the properties of the shell surrounding the filler particles. Three functions of filler distribution have been assumed. Dynamic mechanical properties of a series of vulcanizates were tested and the parameters of the models were computed. The obtained data allows estimating the properties of the shell formed around filler particles in vulcanizates and to distinguish the functions of filler distribution.
Multiple Threshold Percolation in Polymer/Filler Composites
Authors: McQueen Douglas H. , Jäger Karl‐Michael , Paligová Michaela
Published: February 2005

Local variations in filler particle concentration and/or shape and orientation in static filler/polymer composites are modelled as distributions of percolation thresholds. The concentration variations can be due to insufficient mixing, formation of semicrystalline voids during cooling from the melt, shrinkage during polymer curing, flow during physical compression or the like. Irregular filler shapes, especially elongated shapes, reduce the percolation threshold; thus natural variations in the shapes and orientations of filler particle aggregates lead to locally varying percolation thresholds. A distribution of percolation thresholds leads to an apparent percolation threshold based on the conductivity below the mean percolation threshold. For filler concentrations above the apparent percolation threshold the dielectric constant continues to increase before reaching a lowered peak value at the mean percolation threshold and then decreasing. Own experimental results on EBA /carbon black composites support the theory.
Effect of Silica Particle Size on Polymer Adsorption. Morphological, Energetic and Conformational Relationships
Authors: Al Akoum Rami , Haidar Bassel , Vidal Alain
Published: February 2005

A series of six chemically treated and untreated fumed silicas with increasing particle size (ranging from the nano‐ to the micrometer size) was prepared. Surface areas (and morphologies) and surface energies were determined by nitrogen adsorption and inverse gas chromatography, respectively. The adsorption of a series of PDMS with different and well‐defined molecular weights was studied at different polymer concentrations. Amounts of adsorbed polymer were determined by gravimetry and the energies of adsorption were assessed by flow‐microcalorimetry. Results are discussed in terms of particle surface energy and morphology effects on the conformation and the inter‐connectivity of adsorbed polymer molecules.
Bilateral chorea–ballism associated with hyperthyroidism
Authors: Muthipeedika Joy M.A. , Moosa Ahsan , Kumar Anand , Suchowersky Oksana
Published: February 2005

A reply to this letter has been published in Movement DisordersMov Disord (2005) 20 (4) 512.
Cortical cytoskeleton of giant moth eggs
Authors: Jarnot B. , Watson C. , Laffan E. , Nichols L. , Geysen J. , Berry S. J.
Published: February 2005

Unfertilized eggs of several species of giant moths contain a substantial cortical cytoskeleton. This structure is assembled during oogenesis, and contains actin as a major fibrillar component. The presence of actin was confirmed by gel electrophoresis and binding to phalloidin, DNase 1, and a monoclonal antibody against cytoskeletal actin. Several lines of evidence suggest that the fat body is a source of the actin in the oocyte and that the transport and acquisition of actin by the ovary are similar to the mechanism of vitellogenin acquisition. A possible role for the cortical cytoskeleton in directing early embryogenesis is discussed.
Episomal replication of cloned DNA injected into the fertilised ovum of the hen, Gallus domesticus
Authors: Sang Helen , Perry M. M.
Published: February 2005

We describe preliminary experiments to analyse the fate of cloned DNA microinjected into the cytoplasm of the chick fertilised ovum. The reporter gene construct pRSVcat was injected into the germinal disc before the first cleavage divison, and the chick embryos were cultured for up to 7 days using the method of Perry (Nature 331:70–72, 1988). Linear plasmid molecules ligated rapidly after injection to form highmolecular‐weight DNA molecules consisting mainly of random concatemers of the injected plasmid. Recombination involving circular molecules resulted in head‐to‐tail multimers of the plasmid. Some of the DNA was lost after injection, but the remainder was replicated approximately 20‐fold during the first 24 h of development. Between days 1 and 7 in culture, the DNA was gradually lost and diluted out as the embryos developed. By day 7 in culture plasmid DNA was detectable in only 30% of the cultures analysed. No evidence for chromosomal integration of the exogenous DNA was obtained, suggesting that the plasmid DNA persisted episomally. Expression of the reporter gene construct pRSVcat was detected in day 2 and day 7 embryos.
Northern analyses using single‐stranded probes do not support a role for GATA/GACA repeats in sex determination in mice and men
Authors: Durbin Edward J. , Stalvey John R. D. , Erickson Robert P.
Published: February 2005

The possible role of GATA/GACA repeated sequences in mammalian sex determination was investigated using Northern analyses of mouse and human RNA. Brain, liver, and gonadal RNA from three developmental stages of mice of both sexes and also human fetal RNA from various tissues were hybridized to both sense and antisense Bkm riboprobes as well as to the synthetic oligonucleotide (GATA)5. At low levels of stringency, putative transcripts of various sizes were observed in all tissue samples with all probes. At high stringency, only a putative transcript of approximately 12 kb was observed, but this was later shown to consist of contaminating DNA. No sex‐specific differences were observed in any tissue or developmental stage. Thus, we find no evidence that the GATA/GACA repeated sequences are specifically expressed in quantities detectable by Northern analyses in a manner important to mammalian sex determination.
P‐epitope is characteristic for the neural tissue of vertebrates
Authors: Preobrazhensky A. A. , Rodionova A. I. , Barabanov V. M.
Published: February 2005

In a search for antigens immunologically related to chordin, a notochord‐specific glycoprotein of sturgeneous fishes, extracts from 55 samples of human and rabbit tissues were tested for inhibition of [125I]chordin binding to rabbit polyclonal antibodies. The strongest inhibition was observed with brain extracts of both species. Human, chicken, rabbit, and newt brain extracts also inhibited chordin binding in liquid phase to monoclonal antibodies (MAbs) against the P‐epitope, the most immunogenic epitope of this glycoprotein. Immunohistochemical studies done on human and chicken embryos, newt, sterlet, and sturgeon embryos, larvae, and juveniles revealed a strong immunoreactivity of the brain, spinal cord, and tissue of the peripheral nervous system with an anti‐P MAb. Other tissues, with several exceptions, showed a negative reaction in immunohistochemical experiments. The authors found that the P‐epitope is ontogenetically expressed in the neural tissue of chicken, newt, and sterlet at the period of cytodifferentiation. Gel chromatography of human, chicken, and newt brain extracts showed that in each case the P‐epitope was associated with a polydisperse macromolecular material of similar size. These antigens were designated as neurochordins. Prolonged pronase digestion of human and chicken brain extracts resulted in fragments with M about 3 kDa (presumably glycopeptides), which reacted with anti‐P MAbs. These fragments were of the same size as corresponding glycopeptides of the pronase digest of chordin. Thus, in the present study, the P‐epitope has been shown to be characteristic for the neural tissue of several vertebrate species; in the brain, it has been found in association with neurochordins, macromolecular antigens that are presumably protein conjugates with carbohydrates.
Estimates of mRNA abundance in the mouse blastocyst based on cDNA library analysis
Authors: Weng David E. , Morgan Richard A. , Gearhart John D.
Published: February 2005

Studies of gene expression during blastocyst formation in mouse preimplantation development have been limited by the amount of RNA available per embryo. Our present approach to this problem has been to construct a large, representative, blastocyst cDNA library in λgtll. Random hexadeoxynucleotides were used as primers with total blastocyst RNA serving as template. RNA collected from 4,100 32–64 cell embryos was used to generate a library with an initial size of 30 × 106 recombinants. By using clone frequency as a measure of relative mRNA abundance, our data support previous work on the relative and absolute amounts of actin, histone H2a, and intracisternal A particle. Furthermore, we provide estimates for the abundance of cytokeratin endo A, cytokeratin endo B, and β‐tubulin from clone frequency data. Insert sizes for isolated clones range from 200 bp to 3.6 kb with full‐length or near‐full‐length insert sizes for selected clones, indicating that random primer methods generate cDNAs which can represent a significant portion of the mRNA. We have so far characterized products whose abundance is equal to or greater than 0.002% of total RNA. This library offers the potential for the analyses of presumptive regulatory gene products in the mouse preimplantation embryo which are represented as low abundance (<1% of mRNA) RNAs.
Nucleus of the boar spermatozoon: Structure and modifications in frozen, frozen‐thawed, or sodium dodecyl sulfate‐treated cells
Authors: Courtens J. L. , Paquignon M. , Blaise F. , Ekwall H. , Plöen L.
Published: February 2005

After cryosubstitution and Epon embedding, or after Nanoplast embedding and very thin sectioning, the chromatin of ejaculated or diluted boar spermatozoa appears to be formed of DNA fibers embedded in a quite homogeneous matrix. After sodium dodecyl sulfate (SDS) treatment, and to a lesser extent after freeze‐thawing, the DNA fibers are present mostly between cords, probably proteinaceous in nature. The quantity of free sulfhydryl (SH) groups, as calculated from staining by DACM and flow fluorometry, is increased in thawed or SDS‐treated cells. The quantity of NH2 groups, calculated from electron microscopy image analysis of alcoholic phosphotungstic acid‐stained cells, is decreased in thawed nuclei. The DNA is more accessible to the fluorochrome ethidium bromide after freeze‐thawing, and its sensitivity to HCI hydrolysis is modified, during the Feulgen‐like staining procedure using acriflavine. The X‐ray energy dispersive analysis of cryosections of nuclei indicates that the slight separation of DNA and nucleoproteins in freeze‐thawed spermatozoa could result from a dramatic modification of the nuclear ionic environment during thawing.
Measurement of histone mRNA transcript abundance in Xenopus oocytes by a quantitative primer extension assay
Authors: Brashears‐Macatee Sarah , Hinkley Craig , Perry Michael
Published: February 2005

A quantitative primer extension method was used to measure the mass of histone gene transcripts in mature oocytes of the amphibian Xenopus laevis. The procedure, using a large excess of gene‐specific oligonucleotide primer and continuous incorporation of a radiolabeled deoxynucleoside triphosphate precursor, is more sensitive and quantitative than primer extension assays employing end‐labeled primers. It was determined that there are stoichometric amounts, approximately 2 × 108 copies, of mRNA for each of the five major histone gene classes in mature Xenopus oocytes. These observations are consistent with a model whereby transcription of these genes is coordinately regulated in a cell cycle‐independent manner during amphibian oogenesis.
Analysis of the sequence and expression during sea urchin development of two members of a multigenic family, coding for butanol‐extractable proteins
Authors: Carlo Marta Di , Montana Giovanna , Bonura Angela
Published: February 2005

Two cDNA clones related to Paracentrotus lividus butanol‐extracted proteins, presumably belonging to cell surface proteins, were isolated by a λgt11 expression library of ovary poly A+ RNA. These clones, called bep 1 and bep4, of 1,110 and 1,071 bp, respectively, belong to a multigene family. By sequencing analysis, a special structural organization in the coding region is detected. A single copy region is inserted between two regions different from each other but similar in the two clones, which constitute two perfectly preserved domains in the genome and are not always present together in the various members of this gene family. The bep 1 and bep4 clones derive from two single genes that are polymorphic in the sea urchin genome. Expression of these clones was studied by Northern blot analysis. Both bep 1 and bep4 are transcribed during oogenesis into mRNAs of 1.4 kb, which are stored in eggs and utilized during early embryogenesis. None of these RNAs is, in fact, detectable after the gastrula stage. Moreover, the transcripts of three other members of the family are present in eggs and at the 32 cell stage, but they are also synthesized in the early developmental stages.
Relevance to prenatal diagnosis of the identification of a human Y/autosome translocation by Y‐chromosome‐specific in situ hybridisation
Authors: Ellis Patricia M. , West John D. , West Katrine M. , Murray Roderick S. , Coyle M. Christine
Published: February 2005

Routine cytogenetic analysis of an amniotic fluid sample revealed a large brightly fluorescent region in the short arm of chromosome 14 in an otherwise normal male karyotype (46, XY, 14p+++). This site was also present in the paternal karyotype. In situ hybridisation to a Y‐chromosome‐specific DNA probe confirmed that the father had a Y/14 translocation. The incidence of two hybridisation bodies (large hybridisation sites), detecting both the translocated Y chromatin and the normal Y chromosome, was lower in interphase nuclei (44.3%) than in metaphase spreads (95.2%). The relevance of these observations to the potential use of in situ hybridisation to intephase nuclei for prenatal diagnosis is discussed.
Gastrulation in the sea urchin Strongylocentrotus purpuratus is blocked by the fluorescein dye erythrosin B
Authors: Carroll Edward J.
Published: February 2005

Erythrosin B, a food, drug, and cosmetic dye, arrested gastrulation in embryos of the sea urchin Strongylocentrotus purpuratus. A 30 min pulse of 5 μM erythrosin B added at 18 hr postinsemination blocked gastrulation scored at 50 hr postinsemination when control embryos had completed gastrulation. Dye addition at later times had no detectable effects on development through 50 hr postinsemination. The dye may block primary invagination via its known effects on plasma membrane permeability and fluidity.