bluuebunny/crossref_metadata_2025_split huggingface dataset:
Miscibility and phase structure of binary blends of polylactide and poly(methyl methacrylate)
Authors: Zhang Guobao , Zhang Jianming , Wang Shenguo , Shen Deyan 
Published: December 2002

AbstractBlends of amorphous poly(DL‐lactide) (DL‐PLA) and crystalline poly(L‐lactide) (PLLA) with poly(methyl methacrylate) (PMMA) were prepared by both solution/precipitation and solution‐casting film methods. The miscibility, crystallization behavior, and component interaction of these blends were examined by differential scanning calorimetry. Only one glass‐transition temperature (Tg) was found in the DL‐PLA/PMMA solution/precipitation blends, indicating miscibility in this system. Two isolated Tg's appeared in the DL‐PLA/PMMA solution‐casting film blends, suggesting two segregated phases in the blend system, but evidence showed that two components were partially miscible. In the PLLA/PMMA blend, the crystallization of PLLA was greatly restricted by amorphous PMMA. Once the thermal history of the blend was destroyed, PLLA and PMMA were miscible. The Tg composition relationship for both DL‐PLA/PMMA and PLLA/PMMA miscible systems obeyed the Gordon–Taylor equation. Experiment results indicated that there is no more favorable trend of DL‐PLA to form miscible blends with PMMA than PLLA when PLLA is in the amorphous state. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 23–30, 2003
Carbon black‐filled polyolefins as positive temperature coefficient materials: The effect ofin situgrafting during melt compounding
Authors: Hou Yan Hui , Zhang Ming Qiu , Rong Min Zhi 
Published: December 2002

AbstractFor the production of polymer‐based conducting composites serving as positive temperature coefficient (PTC) materials with lower room‐temperature resistivity and sufficiently high PTC intensity, carbon black has been pretreated with acrylic acid and some initiator and then melt‐mixed with low‐density polyethylene. Because of thein situformation of covalent bonding at the filler/matrix interface, the distribution status and thermally induced displacement habit of the conductive fillers have changed accordingly. As a result, the electrical performance of the composites can be tailored as desired. The amount of acrylic acid and the treatment sequence of carbon black exert an important influence on the effectiveness of the modification. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 127–134, 2003
Phase transition in polyamide‐66/montmorillonite nanocomposites on annealing
Authors: Liu Xiaohui , Wu Qiuju , Zhang Qingxin , Mo Zhishen 
Published: December 2002

AbstractThe crystalline‐phase transition in polyamide‐66/montmorillonite nanocomposites before melting was investigated by in situ X‐ray diffraction and is reported for the first time in this work. The phase‐transition temperature in the nanocomposites was 170 °C, 20 °C lower than that in polyamide‐66. The lower phase‐transition temperature of the nanocomposites could be attributed to the γ‐phase‐favorable environment caused by silicate layers. Meanwhile, the addition of silicate layers changed the crystal structure of the polyamide‐66 matrix and influenced the phase‐transition behavior. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 63–67, 2003
Effects of organoclays on morphology and thermal and rheological properties of polystyrene and poly(methyl methacrylate) blends
Authors: Gelfer M. Y. , Song Hyun H. , Liu Lizhi , Hsiao Benjamin S. , Chu Benjamin , Rafailovich Miriam , Si Mayu , Zaitsev Vladimir 
Published: December 2002

AbstractMorphology, thermal and rheological properties of polymer‐organoclay composites prepared by melt‐blending of polystyrene (PS), poly(methyl methacrylate) (PMMA), and PS/PMMA blends with Cloisite® organoclays were examined by transmission electron microscopy, small‐angle X‐ray scattering, secondary ion mass spectroscopy, differential scanning calorimetry, and rheological techniques. Organoclay particles were finely dispersed and predominantly delaminated in PMMA‐clay composites, whereas organoclays formed micrometer‐sized aggregates in PS‐clay composites. In PS/PMMA blends, the majority of clay particles was concentrated in the PMMA phase and in the interfacial region between PS and PMMA. Although incompatible PS/PMMA blends remained phase‐separated after being melt‐blended with organoclays, the addition of organoclays resulted in a drastic reduction in the average microdomain sizes (from 1–1.5 μm to ca. 300–500 nm), indicating that organoclays partially compatibilized the immiscible PS/PMMA blends. The effect of surfactant (di‐methyl di‐octadecyl‐ammonia chloride), used in the preparation of organoclays, on the PS/PMMA miscibility was also investigated. The free surfactant was more compatible with PMMA than with PS; the surfactant was concentrated in PMMA and in the interfacial region of the blends. The microdomain size reduction resulting from the addition of organoclays was definitely more significant than that caused by adding the same amount of free surfactant without clay. The effect of organoclays on the rheological properties was insignificant in all tested systems, suggesting weak interactions between the clay particles and the polymer matrix. In the PS system, PMMA, and organoclay the extent of clay exfoliation and the resultant properties are controlled by the compatibility between the polymer matrix and the surfactant rather than by interactions between the polymer and the clay surface. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 44–54, 2003
Filling‐level effect on the physical properties of MgBr2‐ and MgCl2‐filled poly(vinyl acetate) films
Authors: Zidan H. M. 
Published: December 2002

AbstractThe structural properties of poly(vinyl acetate) (PVAc) films filled with different levels of MgBr2 or MgCl2 were investigated. Differential scanning calorimetry revealed that, at certain filling levels of MgBr2 or MgCl2, two new transitions appeared. The first one was due to the α relaxation (Tα) associated with a crystalline region, and the second was due to the melting temperature (Tm). This implies that a crystalline phase was formed in the polymeric matrix. Changes occurring in Tα, Tm, and the melting peak area as a function of the filling level were examined. The X‐ray diffraction (XRD) pattern revealed that the pure PVAc film was amorphous. However, the addition of MgBr2 or MgCl2 led to the formation of a crystalline phase in the polymeric matrix that depended on the filling level. XRD also demonstrated that the structural changes depended not only on the metal ions but also on the halide ions. Scanning electron microscopy images for the studied samples were examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 112–119, 2003
Screening of some indigenous Qatari medicinal plants for antimicrobial activity
Authors: Mahasneh Adel M 
Published: December 2002

AbstractAqueous, ethanol and butanol crude extracts of the aerial parts of ten plants exhibited variable degrees of antimicrobial activity against four bacterial and two fungal species. Aqueous extracts had low antimicrobial activity against E.coli, P.aeruginosa, B. cerreus, S.aureus, C.albicans and A.flavus. Avicennia marina (AM) aqueous extract exhibited a moderate antifungal activity. Ethanol and butanol crude extracts exhibited an improved antimicrobial activity. However, butanol exhibited a superior antimicrobial activity compared with aqueous and ethanol crudes. Compared with the standard antibiotics tested the butanol extract had the highest activity. Butanol extracts at 2000 μg/disc of AM, Lotus halophilus (LA), Pulicaria gnaphaloides (PG) and Capparis spinosa (CS) had a very good antibacterial activity against both gram‐positive and ‐negative bacteria as well as moderate to good antifungal activity against C. albicans and A. flavus. Medicago laciniata (ML), Limonium axillare (LA) and (PG) butanol crude extract compared with standard chloramphenicol, tetracycline and nalidixic acid exhibited a superior antifungal activity. Copyright © 2002 John Wiley and Sons, Ltd.
Antioxidant and cytotoxic activities of Hypericum sp. on brine shrimps and human cancer cell lines
Authors: Couladis M. , Badisa R. B , Baziou P. , Chaudhuri S. K. , Pilarinou E. , Verykokidou E. , Harvala C. 
Published: December 2002

AbstractTen different samples of five Hypericum sp. were tested on brine shrimps, human colon carcinoma and human hepatoma cell lines for their cytotoxic activities. H. triquetrifolium Turra. (Rafina) showed the highest activity (LC50 = 22 mg/mL) on brine shrimps, while the extracts of the other nine samples showed significant to moderate activities (LC50 from 37 to 107 mg/mL). H. empetrifolium Wild. (Parnon) showed the highest activity in human colon carcinoma and human hepatoma cell lines, with LC50 values 29 and 25.1 mg/mL, respectively, while the LC50 values of the other samples were more than 45 mg/mL. It is very interesting to observe that most Hypericum samples showed good antioxidant activity in vitro. Copyright © 2002 John Wiley & Sons, Ltd.
Composition and antimicrobial activity of the essential oil of Ballota pseudodictamnus L. Bentham
Authors: Couladis M. , Chinou I. B. , Tzakou O. , Loukis A. 
Published: December 2002

AbstractThe chemical composition of the essential oil of Ballota pseudodictamnus obtained from the aerial parts was analysed by GC/MS. From the 52 identified constituents of the oil, caryophyllene oxide, phytol and γ‐muurolene were the major components. Furthermore, the essential oil was investigated for its antimicrobial activity. Copyright © 2002 John Wiley & Sons, Ltd.
Investigation on the wound healing activity of oleo‐resin from Copaifera langsdorffi in rats
Authors: Paiva L. A. F. , de Alencar Cunha K. M. , Santos F. A. , Gramosa N. V. , Silveira E. R. , Rao V. S. N. 
Published: December 2002

AbstractThe wound healing activity of oleo‐resin from Copaifera langsdorffii Desf. (Leguminaceae) bark was evaluated in rats on experimental wounds. The oleo‐resin was tested by monitoring wound contraction in excised wounds and by measuring tensile strength in healing incision wounds. The topical application of oleo‐resin at a concentration of 4% accelerated wound contraction in open wounds. The mean values of wound contraction in oleo‐resin treated rats on day 9 was 84.05% ± 2.37% as against 51.29% ± 9.54% seen in controls and the difference was statistically significant (p < 0.05). No significant differences in the rates of wound contraction were observed on days 12, 15, 18 and 21. Also, the tensile strength in healing incised wounds was found to be significantly higher in the group of animals treated with 4% oleo‐resin on day 5 but not on days 7 and 12 (controls: 35.95 ± 7.44 g/cm; oleo‐resin: 71.48 ± 5.77 g/cm; p < 0.05). These results indicate the beneficial effect of C. langsdorffii oleo‐resin on wound healing and justify its traditional use for the treatment of wounds. Copyright © 2002 John Wiley & Sons, Ltd.
Antioxidant activity of polyphenols from Hypericum triquetrifolium Turra
Authors: Couladis Maria , Baziou Paraskevi , Verykokidou Eumorfia , Loukis Anargyros 
Published: December 2002

AbstractFrom the aerial parts of Hypericum triquetrifolium Turra (Guttiferae) 3‐8″‐biapigenin, quercetin, rutin and chlorogenic acid were isolated. Their structures were elucidated by spectral techniques. Furthermore, the phenolic compounds were tested for antioxidant activity, using an in vitro method based on sodium arachidonoate, bleomycin and thiobarbituric acid with α‐tocopherol as the reference solution. Copyright © 2002 John Wiley & Sons, Ltd.
Antioxidant properties of Indian medicinal plants
Authors: Jadhav Hemant R. , Bhutani K. K. 
Published: December 2002

AbstractThe antioxidant properties of methanol extracts of 12 Indian medicinal plants, traditionally used in disease areas that probably involve free radical mechanisms, were evaluated by two methods, namely the DPPH (1,1‐diphenyl‐2‐picryl hydrazyl) test and the lipid peroxidation assay. In the latter assay, seven of these extracts showed 90% or more activity compared with the standard, vitamin E and hence were studied in detail after the removal of interfering pigments. The selective pigment removal from the extracts led to an increase in free radical scavenging activity and a decrease in inhibition of lipid peroxidation. Copyright © 2002 John Wiley & Sons, Ltd.
Radioprotection of Swiss albino mouse by Centella asiatica extract
Authors: Sharma Jaimala , Sharma Radha 
Published: December 2002

AbstractCentella asiatica, has a considerable reputation in the Indian system of medicine. It is a rasayan (general tonic), brain tonic, improves memory and strengthens the CNS. In view of its multifarious uses, the plant extract was tested for its radioprotective properties. A sublethal dose of Co60 gamma radiation, i.e. 8 Gy was selected for the purpose. Animals were divided into two groups. The whole bodies were irradiated with Co60 gamma radiation externally, with and without drug extract. The drug extract was given orally at different doses and for different time intervals. The dose that was most effective against radiation was 100 mg/kg body weight. This dose increased the survival time of the mice significantly. Body weight loss of the animals in the drug treated group was significantly less in comparison with the animals that were given radiation only. The causes and mechanism of protection and other aspects need further investigations. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of striatal activity in conscious rats: Contribution of NMDA and AMPA/kainate receptors to both spontaneous and glutamate‐driven firing
Authors: Sandstrom Michael I. , Rebec George V. 
Published: December 2002

AbstractSingle‐unit activity in the striatum of unrestrained, conscious rats was characterized by extracellular recording in combination with iontophoresis. To avoid the confounding effect of motor‐related changes in firing rate, measurements were restricted to periods when animals were at quiet rest. Recording electrodes were lowered stepwise through 4.0 mm of anterior striatum in 36 equal ventral movements of 111 μm to assess the ratio of spontaneously active vs. silent neurons. Spontaneous activity was assessed at each step followed by iontophoretic glutamate (GLU) application to expose silent neurons. Eleven such experimental sessions resulted in a total of 100 spontaneously active and 264 silent neurons, indicating that without overt movement the large majority (72.7%) of striatal cells are silent. Spontaneously active neurons, moreover, discharged at low rates (4.85 ± 0.85 spikes/s). In separate experiments, both the AMPA/kainate (CNQX: 6‐cyano‐2,3‐dihydroxy‐7‐nitro‐quinoxaline disodium salt) and NMDA (AP5: D‐(‐)‐2‐amino‐5‐phosphonovaleric acid) GLU‐receptor antagonists blocked the activity of most spontaneously active (83% CNQX, 69% AP5), and GLU‐stimulated silent (68% CNQX, 98% AP5) units. Collectively, our results are consistent with an overall low level of striatal activity in the absence of strong excitatory input. When neuronal activity is initiated, however, it appears that both NMDA and AMPA/kainate receptors are critical for maintaining continuous impulse activity. Synapse 47:91–100, 2003. © 2002 Wiley‐Liss, Inc.
Role of Giα2‐protein in opioid tolerance and μ‐opioid receptor downregulation in vivo
Authors: Yoburn B.C. , Gomes B.A. , Rajashekara V. , Patel C. , Patel M. 
Published: December 2002

AbstractAlthough opioid receptors are G‐protein coupled, the role that specific G‐protein subunits play in the development of opioid tolerance and the regulation of opioid receptor number is not well understood. In the present study, we used a Giα2 antisense oligodeoxynucleotide (ODN) to examine the contribution of Giα2 proteins to μ‐opioid tolerance and receptor downregulation in the mouse. Mice were injected intracerebroventricularly (ICV) and into the spinal intrathecal space (IT) for 4–5 consecutive days (30 μg/site/day), with an antisense ODN or a mismatch ODN directed at mRNA for the Giα2 subunit of G‐proteins. Controls were treated with dH2O. On the second day of ODN treatment continuous subcutaneous (SC) infusion of etorphine (200 μg/kg/day) or morphine (40 mg/kg/day + 25 mg pellet) was begun. Control mice were implanted with inert placebo pellets. Three days later, pumps and pellets were removed and mice were tested for morphine analgesia or μ‐opioid receptor density was determined in whole brain. Etorphine produced significant tolerance (ED50 shift = ∼11‐fold) and downregulation of μ‐opioid receptors (≈25%). Morphine treatment produced significant tolerance (ED50 shift ≈9‐fold), but no μ‐opioid receptor downregulation. Antisense treatment reduced Giα2 protein levels in striatum and spinal cord by ∼25%. Giα2 antisense reduced the acute potency of morphine. Giα2 antisense blocked the development of tolerance to morphine treatment and reduced the development of tolerance to etorphine treatment. Antisense did not have any effect on etorphine‐induced μ‐opioid receptor downregulation. In another experiment, 7‐day treatment with morphine or etorphine similarly increased Giα2 mRNA and protein abundance in spinal cord. Overall, these results support an important role for Giα2‐protein in the acute effects of opioids and opioid tolerance. However, Giα2 is not required for agonist‐induced μ‐opioid receptor density regulation in vivo. Synapse 47:109–116, 2003. © 2002 Wiley‐Liss, Inc.
Locomotor inhibition induced by procaine injections into the nucleus accumbens core, but not the medial ventral striatum: Implication for cocaine‐induced locomotion
Authors: Ikemoto Satoshi , Witkin Brian M. 
Published: December 2002

AbstractWe examined whether injections of the local anesthesia procaine into the nucleus accumbens core disrupts locomotion more readily than those into the medial ventral striatum. Spontaneous locomotion decreased during the first 10 min immediately following injections of procaine into the core. When procaine was co‐administered with d‐amphetamine into the core, the injections also decreased amphetamine‐induced locomotion during the initial 10 min. On the other hand, no detectable effect on spontaneous or amphetamine‐induced locomotion was found when procaine was injected into the medial ventral striatum, including the medial shell and medial olfactory tubercle. We replicated our recent finding that cocaine injections into the core induced delayed, modest locomotion, while cocaine injections into the medial ventral striatum induced immediate, vigorous locomotion. Injections of amphetamine into the core induced as equally vigorous locomotion as that of the medial ventral striatum. These results show that the neurons of the core involved in locomotion are more vulnerable to local anesthesia than the neurons of the medial ventral striatum. In other words, cocaine at the doses inducing vigorous locomotion in the medial ventral striatum induces local anesthesia when applied to the core. Synapse 47:117–122, 2003. Published 2002 Wiley‐Liss, Inc.
Purinergic modulation of neuronal activity in the mesolimbic dopaminergic system in vivo
Authors: Krügel Ute , Kittner Holger , Franke Heike , Illes Peter 
Published: December 2002

AbstractATP and its metabolite adenosine activate membrane receptors, termed P2 and P1, respectively. In the present study, the modulation of the mesolimbic neuronal circuit by ATPergic and adenosinergic mechanisms was investigated by microdialysis in the nucleus accumbens (NAc) and by telemetrically recorded EEG from both the NAc and the ventral tegmental area (VTA) of freely moving rats. The basal extracellular dopamine concentration was enhanced after accumbal perfusion with the ATP analog 2‐methylthio ATP (2‐MeSATP; 100 μM); by contrast, adenosine (100 μM) caused a reduction of extracellular dopamine. When given alone, the P2 receptor antagonist pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS; 20 μM) decreased the concentration of dopamine, whereas the P1 receptor antagonist 8‐(p‐sulfophenyl)theophylline (8‐SPT; 100 μM) increased it. In the same animals, P2 receptor stimulation by 2‐MeSATP caused neuronal activation, indicated by an elevation of the absolute power in the EEG of the NAc mainly by enhancement of the relative power in the alpha band (8–13 Hz) of the EEG spectrum. By contrast, adenosine led to a depression of the absolute power in the VTA accompanied by an elevation of the delta‐band power (0.4–6 Hz) in the NAc corresponding to a slowing of neuronal activity. When given alone, PPADS reduced the absolute EEG power in the NAc accompanied by a decrease in the high‐frequency power, but had no effects on the VTA. 8‐SPT on its own enhanced the total power in both the NAc and the VTA, reflected by an enhancement in the slow and the high‐frequency bands. Whereas the 8‐SPT‐evoked changes of EEG pattern as well as of dopamine concentration in the NAc were abolished by the co‐application of PPADS, the 8‐SPT‐induced EEG changes in the VTA persisted under these conditions. In conclusion, the accumbal neuronal output, reflected by both dopamine release and neuronal electrical activity, is modulated in a functionally antagonistic manner by P2 and P1 receptor stimulation. It is suggested that an inhibitory GABAergic feedback projection to the VTA is stimulated by adenosine, either directly or indirectly via glutamate release. Synapse 47:134–142, 2003. © 2002 Wiley‐Liss, Inc.
Positron emission tomography imaging of the serotonin transporter in the pig brain using [11C](+)‐McN5652 and S‐([18F]fluoromethyl)‐(+)‐McN5652
Authors: Brust Peter , Zessin Jörg , Kuwabara Hiroto , Pawelke Beate , Kretzschmar Marion , Hinz Rainer , Bergman Jörgen , Eskola Olli , Solin Olof , Steinbach Jörg , Johannsen Bernd 
Published: December 2002

AbstractS‐([18F]fluoromethyl)‐(+)‐McN5652 ([18F](+)‐FMe‐McN5652) has recently been synthesized as a new potential radiotracer for positron emission tomography (PET) imaging of the 5‐HT transporter. It is an analog of [11C](+)McN5652, which has been used in clinical PET studies for 5‐HT transporter imaging. This article describes the comparison of these two radiotracers in pigs with respect to their in vivo binding characteristics. PET images revealed that the highest accumulation of both radiotracers was found in the ventral midbrain, thalamus, olfactory lobe, and pons which is consistent with the known density of 5‐HT transporters. The specific binding was determined by subtracting the values of the inactive (−) enantiomers or of the occipital cortex from those obtained with [11C](+)McN5652 or [18F](+)‐FMe‐McN5652 in the time period between 75 and 115 min after radiotracer injection. The specific binding of the 18F‐labeled derivative was about 40% higher than that of the 11C‐labeled derivative. A strong inhibition of the specific binding was observed for both radiotracers after pretreatment with the selective 5‐HT uptake inhibitor citalopram. [18F](+)‐FMe‐McN5652 showed faster kinetics than [11C](+)McN5652. It reached the binding equilibrium during a study length of 120 min, which was not the case for [11C](+)McN5652. It is concluded that [18F](+)‐FMe‐McN5652 is suitable for 5‐HT transporter imaging with PET. Synapse 47:143–151, 2003. © 2002 Wiley‐Liss, Inc.