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61.
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The purpose of this study was to investigate the physicochemical properties of nonpareil beads coated with Eudragit RS 30 D containing ibuprofen as a multifunctional agent. The influence of the concentration of ibuprofen in the film coating and the effect of the coating level on drug release from coated beads was determined in pH 7.2 phosphate buffer solution. The influence of storage time at 23 degrees C and 60 degrees C on the release of ibuprofen from coated beads was also investigated. The thermal properties of the films were determined using a differential scanning calorimeter. Scanning electron microscopy was employed to image the surface morphology of the coated beads. Infrared spectroscopy was used to study the interaction of Eudragit RS 30 D and ibuprofen. Results from the dissolution studies demonstrated that increasing the amount of ibuprofen in the polymeric film reduced the rate of drug release, mainly because of a more complete coalescence of the polymeric particles of the latex dispersion. The glass transition temperature (Tg) of Eudragit RS 30 D films decreased and the surface of the coated beads became smoother as the concentration of ibuprofen was increased. Hydrogen bonding between the polymer and ibuprofen was demonstrated by Fourier transform infrared spectroscopy. No significant differences were found in drug dissolution between the coated beads stored at 23 degrees C for 12 months and those stored at 60 degrees C for 12 hours. The results of this study demonstrated that the ibuprofen plasticized the Eudragit RS 30 D. Furthermore, the dissolution rate of ibuprofen can be controlled and changes in the drug release rate can be minimized by using the drug-induced plasticization technique with this polymer. 相似文献
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A newly available polyvinylacetate aqueous dispersion, Kollicoat SR 30D, was evaluated with respect to its ability to modulate
the in vitro release of a highly water-soluble model compound (diphenhydramine hydrochloride) from nonpareil-based systems.
Kollicoat SR 30D premixed with a selected plasticizer (10% wt/wt propylene glycol, 2.5% triethyl citrate, or 2.5% dibutyl
sebacute), talc, and red #30 lake dye was coated onto the drug beads in an Aeromatic Strea I fluid-bed drier with a Wurster
insert using bottom spray. With propylene glycol as the plasticizer, increases in polymer coating level retarded drug release
from beads in a stepwise fashion along with apparent permeability, indicating a consistent release mechanisms. Stability studies
at 40°C/75% RH revealed gradual decreases in dissolution rate, and additional curing studies further confirmed the dependence
of release kinetics on curing condition. Furthermore, the type of plasticizer was found to play a key role. Unplasticized
formulations exhibited the fastest dissolution, followed by formulations plasticized with triethyl citrate, propylene glycol,
and dibutyl sebacate. All 4 formulations (unplasticized and plasticized), nevertheless, revealed a marked difference between
uncured and cured dissolution profiles. Kollicoat SR 30D has, thereby, been demonstrated to effectively retard drug release
from nonpareilbased systems. However, selected plasticizer type and subsequent curing condition play important roles in controlling
drug release from such a system. 相似文献
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Two novel crystal protein genes from a highly mosquitocidal Bacillus thuringiensis serovar medellin strain were cloned and sequenced. The corresponding proteins, Cry29A and Cry30A, were nontoxic when tested individually against the mosquito species bioassayed (Aedes aegypti, Culex pipiens and Anopheles stephensi). However, Cry29A synergized the toxicity of Cry11Bb against Aedes aegypti by a four-fold factor. 相似文献
68.
Zine A 《Molecular neurobiology》2003,27(2):223-237
Mechanosensory hair cells of the vertebrate cochlea offer an excellent developmental system to study cell-fate specification,
and to gain insight into the many human neurological deficits which result in a hearing loss, by affecting primarily the hair
cells. Therefore, there is great interest in studying the molecular mechanisms that regulate their specification and differentiation.
Recent studies, based mostly on loss-of-function experiments that target the role of Notch signaling and basic helix-loop-helix
genes in inner-ear development have indicated that they can regulate mechanosensory hair cell-fate specification and their
initial differentiation. 相似文献
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Hideo Mukai Tetsuya Kimoto Yasushi Hojo Suguru Kawato Gen Murakami Shimpei Higo Yusuke Hatanaka Mari Ogiue-Ikeda 《Biochimica et Biophysica Acta (BBA)/General Subjects》2010
The hippocampus is a center for learning and memory as well as a target of Alzheimer's disease in aged humans. Synaptic modulation by estrogen is essential to understand the molecular mechanisms of estrogen replacement therapy. Because the local synthesis of estrogen occurs in the hippocampus of both sexes, in addition to the estrogen supply from the gonads, its functions are attracting much attention. 相似文献