Using physiological tests on the selection of cut roses' varieties

We have observed that the evolution of the senescence in vase can be appreciated by the measures of pH, conductivity, or osmolarity of the petal cell sap of a rose variety. We wanted to check whether these physiological tests could be used to select the post-harvest quality of varieties in process of evaluation. Whereas the measures of pH and osmolarity do not seem to be correlated with the flower's vase life, those of conductivity seem to be linked to it (r=-0.74). As far as the pH is concerned, when the correlation is tested on varieties grouped in colours (white, yellow and ochre; pink and red; multicoloured) and not on the whole mixed varieties, then the correlation seems to be satisfactory, being characterized by r coefficients between -0.78 and -0.91.     

Mechanism and substrate specificity of the flavin reductase ActVB from Streptomyces coelicolor

ActVB is the NADH:flavin oxidoreductase participating in the last step of actinorhodin synthesis in Streptomyces coelicolor. It is the prototype of a whole class of flavin reductases with both sequence and functional similarities. The mechanism of reduction of free flavins by ActVB has been studied. Although ActVB was isolated with FMN bound, we have demonstrated that it is not a flavoprotein. Instead, ActVB contains only one flavin binding site, suitable for the flavin reductase activity and with a high affinity for FMN. In addition, ActVB proceeds by an ordered sequential mechanism, where NADH is the first substrate. Whereas ActVB is highly specific for NADH, it is able to catalyze the reduction of a great variety of natural and synthetic flavins, but with K(m) values ranging from 1 microm (FMN) to 69 microm (lumiflavin). We show that both the ribitol-phosphate chain and the isoalloxazine ring contribute to the protein-flavin interaction. Such properties are unique and set the ActVB family apart from the well characterized Fre flavin reductase family.     

Solution structure of the R3H domain from human Smubp-2

The R3H domain is a conserved sequence motif, identified in over 100 proteins, that is thought to be involved in polynucleotide-binding, including DNA, RNA and single-stranded DNA. In this work the 3D structure of the R3H domain from human Smubp-2 was determined by NMR spectroscopy. It is the first 3D structure determination of an R3H domain. The fold presents a small motif, consisting of a three-stranded antiparallel beta-sheet and two alpha-helices, which is related to the structures of the YhhP protein and the C-terminal domain of the translational initiation factor IF3. The similarities are non-trivial, as the amino acid identities are below 10%. Three conserved basic residues cluster on the same face of the R3H domain and could play a role in nucleic acid recognition. An extended hydrophobic area at a different site of the molecular surface could act as a protein-binding site. A strong correlation between conservation of hydrophobic amino acids and side-chain solvent protection indicates that the structure of the Smubp-2 R3H domain is representative of R3H domains in general.     

The FliS chaperone selectively binds the disordered flagellin C-terminal D0 domain central to polymerisation

Assembly of each Salmonella typhimurium flagellum filament requires export and polymerisation of ca. 30000 flagellin (FliC) subunits. This is facilitated by the cytosolic chaperone FliS, which binds to the 494 residue FliC and inhibits its polymerisation. Yeast two-hybrid assays, co-purification and affinity blotting showed that FliS binds specifically to the C-terminal 40 amino acid component of the disordered D0 domain central to polymerisation. Without FliS binding, the C-terminus is degraded. Our data provide further support for the view that FliS is a domain-specific bodyguard preventing premature monomer interaction.     

Influence of age,castration, and testosterone on T cell subsets in healthy and leukemia grafted mice

The distribution of T cell subsets in pubertal (2 months) and post-pubertal (10 months) mice showed a significant decrease in the percentage of CD4+ splenocytes and peripheral blood lymphocytes (PBL) with age, unlike the percentage of CD8+ cells in PBL, which remained unchanged. The change in the distribution of T cell subsets in the spleen and blood occurred in 2 months old castrated mice, as in 10 months old animals. P388 tumor grew better in post-pubertal and in castrated mice than in young mice. The intact mice survived longer than the castrated ones. The relative number of CD4+, CD8+ and CD2+ splenocytes was lower in transplanted intact mice than that in controls. The CD8+ and CD2+ subsets in the blood of 2 months transplanted mice were higher than those in controls, whereas in PBL, in 10 months old and castrated mice, the T lymphocyte subsets remain unchanged. Depo-testosterone (DT) injection strongly reduced weight and tumor growth in all the intact and castrated animals. A significant correlation is observed between the tumor weight and testosterone level in the plasma of the 2 months old DT treated mice. Moreover, DT injection induced a significant increase in the percentage of blood CD8+ cells in all the batches. These data indicate that physiologically, androgens affect the age-related distribution of lymphocyte T subsets and suggest that they slow down tumor growth, besides causing a direct effect, through an immunological process.     

MyoD, Myogenin, and Desmin-nls-lacZ Transgene Emphasize the Distinct Patterns of Satellite Cell Activation in Growth and Regeneration

Although satellite cell differentiation is involved in postnatal myogenesis from growth to posttrauma regeneration, the early stages of this process remain unclear. This study investigatedpHuDes-nls-lacZtransgene activity, as revealed by X-gal staining and the accumulation of MyoD, myogenin, endogenous desmin, and myosin, in order to determine whether satellite cells share the same activation program during growth and regeneration. After birth, skeletal myonuclei in which myogenin expression was limited were briefly characterized by transgene activity. Satellite cells were only evidenced by MyoD and slow myosin accumulation, but failed to initiate transgene expression. After freeze trauma, satellite cell activation led to MyoD, myogenin, and desmin expression. Subsequently, when myosin expression occurred, transgene activation was apparent in regenerating structures, with more intense X-gal staining in mononucleated cells than regenerating myotubes. After the second week posttrauma, only desmin and myogenin expression were maintained in regenerating structures. In culture, the behavior of satellite cells showed that desmin expression was committed before transgene activation occurred, i.e., concurrently with MyoD, myogenin, myosin expression, and the first fusion events. Quantitative analysis confirmed the discrepancy between endogenous desmin and transgene expression and demonstrated the close correlation between transgene activation and the fusion index. Our results strongly suggest that satellite cells promote distinct pathways of myogenic response during growth and regeneration.