PubMed · 4532385
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G Roderwald, D Zukunft. 1974. [Some toothcolored plastics].. https://pubmed.ncbi.nlm.nih.gov/4532385/
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Growth cones are required for the forward advancement and navigation of growing axons. Modulation of growth cone shape and reorientation of the neurite are responsible for the change of outgrowth direction that underlies navigation. Change of shape involves the reordering of the cytoskeleton. Reorientation of the neurite requires the generation of tension, which is supplied by the ability of the growth cone to crawl on a substrate. The specific molecular mechanisms responsible for these activities are unknown but are thought to involve actomyosin-generated force combined with linkage to the cell surface receptors that are responsible for adhesion (Heidemann and Buxbaum, 1998). To test whether myosin IIB is responsible for the force generation, we quantified shape dynamics and filopodial-mediated traction force in growth cones from myosin IIB knock-out (KO) mice and compared them with neurons from normal littermates. Growth cones from the KO mice spread less, showed alterations in shape dynamics and actin organization, and had reduced filopodial-mediated traction force. Although peak traction forces produced by filopodia of KO cones were decreased significantly, KO filopodia occasionally developed forces equivalent to those in the wild type. This indicates that other myosins participate in filopodial-dependent traction force. Therefore, myosin IIB is necessary for normal growth cone spreading and the modulation of shape and traction force but acts in combination with other myosins for some or all of these activities. These activities are essential for growth cone forward advancement, which is necessary for outgrowth. Thus outgrowth is slowed, but not eliminated, in neurons from the myosin IIB KO mice.
The object of our work is the preparation of a mucoadhesive drug delivery system intended for intravesical application. In the present work, microspheres with Eudragit RS matrix polymer and different mucoadhesive polymers, i.e. chitosan hydrochloride (Ch), sodium salt of carboxymethyl cellulose (CMC) and polycarbophil (PC) were prepared to evaluate their influence on the mucoadhesive properties of microspheres. Different parameters were determined and their influence on pipemidic acid release from microspheres adhered on intact and damaged pig vesical mucosa was evaluated: swelling of polymers, mucoadhesion strength of polymeric films and drug dissolution according to USP XXIV method. The dissolution rate from microspheres containing different mucoadhesive polymers decreases as follows: PC>Ch>CMC. PC swelled to the largest volume among all polymers and as a result the fastest release of the drug from PC microspheres was obtained. The release rate of pipemidic acid from microspheres adhered on intact mucosa followed the order PC>CMC>Ch. These results show that both drug dissolution and mucoadhesion strength strongly influence drug release from adhered microspheres. The slowest release from Ch microspheres could be interpreted by the largest mucoadhesion strength of Ch polymeric films. The release rate of pipemidic acid from microspheres adhered on damaged mucosa followed the order PC=Ch>CMC. The results obtained on pathologically changed mucosa model support the indication of the role of glycosaminoglycans and polymer charge in the mucoadhesion process on vesical mucosa. Analysis of release data shows that the drug dissolution profiles follow the Higuchi kinetics better than the release profiles from adhered microspheres and different kinetics might be a consequence of different release mechanisms.
A novel method was used to examine the microbial ecology of iron-rich wetland sediments receiving neutral-pH coal mine drainage. Gel probes inserted into the sediments allowed analysis of the distribution and activity of bacterial sulfate reduction (BSR). A mixed population of sulfate-reducing bacteria enriched from anoxic wetland sediments was immobilized in low temperature-gelling agarose held in grooved rods or probes. The probes were inserted vertically into sediments and were allowed to incubate in situ for 48 h. After their retrieval, the gels were sectioned and analyzed for residual BSR activity and were compared to in situ BSR rates and chemical porewater profiles. The depth distribution of residual BSR activity in the immobilized cell gel probes differed significantly from the BSR measured in situ. Approximately 51% of the total integrated residual sulfate reduction activity measured in the gel probes occurred between 0 and 7 cm of the upper 20 cm of sediment. In contrast, ca. 99% of the integrated in situ BSR occurred between 7- and 20-cm depth, and only 1% of the total integrated rate occurred between 0- and 7-cm depth. Lactate-enriched bacteria immobilized in the gel may have been atypical of the majority of sulfate-reducing bacteria in the sediment. Agarose-immobilized sulfate-reducing bacteria might also be able to proliferate in the otherwise inhospitable zone of iron reduction, where sulfate and labile carbon compounds for which they are usually outcompeted can diffuse freely into the gel matrix. Gel probes containing particulate iron monosulfide (FeS) indicated that FeS remained stable in sediments at depths greater than 2 to 3 cm below the sediment-water interface, consistent with the shallow penetration of oxygen into surface sediments.