Differential behavior of (25R)-5,6-epoxyspirostan-22 alpha-O-3 beta-ol and (25R)-5,6-epoxyspirostan-22 alpha-O-3 beta, 4 beta-diol toward Dowex

The acid-catalyzed hydrolytic cleavage of the 5,6-epoxyspirostane derivatives by the cation exchange resin Dowex 50W X8 has been exploited with the goal of developing synthetic protocols toward 3,4,5,6-polyhydroxyspirostane analogs that can serve as intermediates to potential biologically active compounds. Whereas the diastereomers (25R)-5 alpha, 6 alpha-epoxyspirostan-22 alpha-O-3 beta-ol and (25R)-5 beta, 6 beta-epoxyspirostan-22 alpha-O-3 beta-ol yield two products, (25R)-6 beta-methoxyspirostan-22 alpha-O-3 beta, 5 alpha-diol and (25R)-spirostan-22 alpha-O-3 beta, 5 alpha, 6 beta-triol on Dowex treatment in water-methanol, the alpha- and beta-diastereomers of the 5,6-epoxy derivative of 3 beta, 4 beta-diol provide a single product, (25R)-3 beta, 6 beta-dihydroxy-5 alpha-spirostan-4-one, in good yields. The structures of these products have been confirmed using 1H NMR, 13C NMR, and 1H-1H J-correlated spectroscopies. Multifunctional product formation suggests tremendous utility of Dowex in steroid synthesis. The product formation has been rationalized on the basis of differential conformational constraints of the A/B rings of the different epoxides in directing the reaction course. The reaction shows an interesting example of stereoelectronic effect of a single hydroxy group in discriminating solvent participation.     

The effect of live measles vaccines on serum vitamin A levels in healthy children

In chordate phylogeny, changes in the nervous system, jaws, and appendages transformed meek filter feeders into fearsome predators. Gene duplication is thought to promote such innovation. Vertebrate ancestors probably had single copies of genes now found in multiple copies in vertebrates and gene maps suggest that this occurred by polyploidization. It has been suggested that one genome duplication event occurred before, and one after the divergence of ray-finned and lobe-finned fishes. Holland et al., however, have argued that because various vertebrates have several HOX clusters, two rounds of duplication occurred before the origin of jawed fishes. Such gene-number data, however, do not distinguish between tandem duplications and polyploidization events, nor whether independent duplications occurred in different lineages. To investigate these matters, we mapped 144 zebrafish genes and compared the resulting map with mammalian maps. Comparison revealed large conserved chromosome segments. Because duplicated chromosome segments in zebrafish often correspond with specific chromosome segments in mammals, it is likely that two polyploidization events occurred prior to the divergence of fish and mammal lineages. This zebrafish gene map will facilitate molecular identification of mutated zebrafish genes, which can suggest functions for human genes known only by sequence.     

Sugar cross-linked gelatin for controlled release: microspheres and disks

The aim of the present paper was to find a 'biocompatible' means to cross-link gelatin-based pharmaceutical devices. In particular, we have studied the ability of native and oxidized mono- and di-saccharides to induce the cross-linking of gelatin. To this end, gelatin discs and gelatin microspheres were produced and their dissolution kinetics at 37 degrees C were examined. In order to find evidence of sugar-mediated cross-linking, DSC and FTIR experiments were performed. The obtained results indicated that both native and oxidized sugars resulted to different extents, in the formation of a cross-linked gelatin network able to reduce the dissolution of gelatin. These results suggest that oxidized mono- and disaccharides could be an interesting method by which to cross-link gelatin thereby reducing the risk of toxic side effects arising from the use of synthetic cross-linkers.     

Unusual immunocytochemical and ultrastructural features of synovial fluid cells in multicentric reticulohistiocytosis. A case report

We present the first report in which cells in synovial fluid from a patient with multicentric reticulohistiocytosis (MRH) were studied by immunocytochemistry for correlation with routine light and electron microscopy. MRH cells stained predominantly for lymphocyte-related surface antigens and not for the monocyte marker LEU M3 (CD14). These findings suggest a lymphocytic origin of MRH cells and not a histiocytic origin, as previously suggested. In addition, large numbers of membrane-bound, electron-dense, secretory-type granules were found ultrastructurally in the cytoplasm of these cells.     

Investigation of fusion welded butt joints in structural steels

In the present paper research work is presented combining material related research, weld fabrication related research and research in the field of numerical analysis of welded joint performance. Elements belonging to this extensive combination are mechanical testing, fracture mechanics testing of small scale and full thickness specimens, component testing including engineering defect assessment and numerical modelling using finite element method. Examples are given for each of the above mentioned elements.