PubMed · 10786183
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R G Ritter. 1999. Advanced adhesive technology.. https://pubmed.ncbi.nlm.nih.gov/10786183/
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Sustained-release nitrendipine microspheres were prepared in liquid system by quasi-emulsion solvent diffusion method, in which the Aerosil was employed as an inert dispersing carrier to improve the dissolution rate of nitrendipine, and Eudragit RS as a retarding agent to control the release rate. The resultant microspheres were evaluated for the recovery, bulk density, average particle size, drug loading, and incorporation efficiency. And the factors affecting the formation of microspheres and the drug-release rate were investigated. It was observed by a scanning electron microscope (SEM) that the microspheres were finely spherical and uniform, and no entire nitrendipine crystals were observed visually. The results of X-ray diffraction indicated that nitrendipine in microspheres was disordered, suggesting that nitrendipine was highly dispersed in microspheres. The drug loading of microspheres was enhanced with increasing the ratio of drug to excipients, and the incorporation efficiency was always >90%. The formation of microspheres was mainly influenced by the amount of bridging liquid and sodium dodecyl sulfate (SDS) in poor solvent. The dissolution profiles could be modulated with adjusting the amount of retarding agent and dispersing carrier formulated.
The unique nature of vestibular otoconia as calcium carbonate biominerals makes them particularly susceptible to chemical deformation during histological processing. We fixed and stored otoconia from all three otolith endorgans of embryonic, hatchling and adult Japanese quail in glutaraldehyde containing either phosphate or non-phosphate buffers for varying lengths of time and processed them for scanning electron microscopy. Otoconia from all age groups and otolith endorgans processed in 0.1 M phosphate buffer (pH 7.4) showed abnormal surface morphology when compared to acetone fixed controls. Otoconia processed in 0.1 M sodium cacodylate or HEPES buffered artificial endolymph (pH 7.4) showed normal morphology that was similar to controls. The degree of otoconial deformation was directly related to the time exposed to phosphate buffer. Short duration exposure produced particulate deformations while longer exposures resulted in fused otoconia that formed solid sheets. Otoconial surface deformation and fusing was independent of the glutaraldehyde component of the histological processing. These findings should help vestibular researchers to develop appropriate histological processing protocols in future studies of otoconia.
The high solvent phenotype of Clostridium acetobutylicum mutants B and H was complemented by the introduction of a plasmid that contains either an intact or partially-deleted copy of solR, restoring acetone and butanol production to wild-type levels. This demonstrates that the solR open reading frame on pSOLThi is not required to restore solvent levels. The promoter region upstream of alcohol dehydrogense E (adhE) was examined in efforts to identify sites that play major roles in the control of expression. A series of adhE promoter fragments was constructed and the expression of each in acid- and solvent-phases of growth was analyzed using a chloramphenicol acetyl-transferase reporter system. Our results show that a region beyond the 0A box is needed for full induction of the promoter. Additionally, we show that the presence of sequences around a possible processing site designated S2 may have a negative role in the regulation of adhE expression.