Search

The complete understanding of the morphological differentiation of streptomycetes is an ambitious challenge as diverse sensors and pathways sensitive to various environmental stimuli control the process. Germination occupies a particular position in the life cycle as the good achievement of the process depends on events occurring both during the preceding sporulation and during germination per se. The cyclic AMP receptor protein (crp) null mutant of Streptomyces coelicolor, affected in both sporulation and germination, was therefore presented as a privileged candidate to highlight new proteins involved in the shift from dormant to germinating spores. Our multidisciplinary approach&sbd;combining in vivo data, the analysis of spores morphological properties, and a proteome study&sbd;has shown that Crp is a central regulatory protein of the life cycle in S. coelicolor; and has identified spores proteins with statistically significant increased or decreased expression that should be listed as priority targets for further investigations on proteins that trigger both ends of the life cycle. Keywords: ADP-ribosylation • cAMP • Crp • germination • morphological differentiation • spore • streptomycetes

We used scanning electron microscopy in combination with Xray microanalysis to evaluate Co, Cr, and Mobased human femoral hip prostheses. In total, 23 retrieved implants and four new implants were included in this study. Scanning electron microscopy of the polished surface of all arthroplasties showed, in addition to the polishing marks, small round and angular holes or pits. Other types of surface irregularities were interpreted as wear or corrosion of the metal compound. In all cases studied, corrosion propagated from holes at the surface of the polished prosthesis heads, in some cases also along phase boundaries. Xray microanalysis of the intact prosthetic surface showed a relative composition of the elements Co, Cr, and Mo, which was in agreement with the manufacturers information 63:33:4. However, Xray microanalysis spot analysis of the surface holes showed deviation in the relative composition of the elements Co, Cr, and Mo and also the presence of Si, Ti, and Al. Furthermore, Ti and Al could be traced back at an artificially made fracture plane of a new prosthesis. Therefore, Ti and Al have to be present during the manufacturing process. These impurities in the metal prosthesis alloy may create a galvanic element with the Co, Cr, Mo alloy of the implant. If this is the case, such a galvanic element in combination with the electrolyte environment formed by body fluids, can induce galvanic corrosion with release of metal particles. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res 54: 591–596, 2001

As part of a study of the antigenic composition of the tegument of mechanically transformedSchistosoma mansoni schistosomula, the phenomenon of coat formation around such schistosomula when incubated in medium containing serum ofS. mansoni infected mice was investigated with light and scanning electron microscopy.

The barrier function of the skin resides in the stratum corneum (SC). This outermost layer consists of protein-rich corneocytes and lipid-rich intercellular domains. These domains form the rate-limiting step for transepidermal water loss and the penetration of substances from the environment. To study the nature of the barrier function, stratum corneum lipid models have been examined with wide-angle X-ray diffraction. A disadvantage of this technique is that it requires bulk quantities of lipid and thus information on variations in the lateral packing cannot be obtained in the microm-range. To the best of our knowledge, this is the first study in which electron diffraction is applied on SC lipid model systems. Using this technique, local structural information was obtained about mixtures prepared from isolated pig ceramides, cholesterol, and long-chain free fatty acids. It appeared that addition of free fatty acids caused a transition from a hexagonal to an orthorhombic packing and that electron diffraction can be applied to distinguish between these two lattices. The results are in good agreement with wide-angle X-ray diffraction data and suggest that application of electron diffraction in skin studies can provide new information on the lipid organization in well-defined areas of the stratum corneum.

Aerodynamically, grass-pollen grains should be filtered from the inhaled air in the nose. They should not penetrate into the deeper airways (bronchi, bronchioles). Yet, bronchial symptoms are not seldom seen in patients suffering from pollinosis. Therefore, the grass-pollen allergenic activity of the smaller, paucimicronic atmospheric aerosol fraction was studied. Outdoor airborne particulate matter was collected and separated into fractions according to aerodynamic sizes (> 10; 4.9-10; 2.7-4.9; 1.3-2.7; 0.6-1.3; < 0.6 μm), with a Cascade Impactor mounted on top of a high volume sampler. The different fractions were tested for the presence of grass-pollen allergenic activity using a RAST-inhibition assay. The results show that on days with a relatively high grass-pollen count, a considerable amount of allergen was present in all the smaller micronic aerosol fractions.