Persistence of chromosomal lesions induced in actively proliferating bone marrow cells of the mouse.

The persistence of chromosomal lesions induced in vivo by mitomycin C (MMC) was evaluated by cytogenetic analysis of mouse bone marrow cells. Chromosome aberration (CA) and micronucleus (MN) frequencies were estimated at different times after treatment, up to 42 days. The frequency of CA per cell decreased in the first 3 days after treatment, but a secondary peak appeared on the 4th day, followed by a stabilization around 0.03 CA per cell (significantly different from the control value), which persisted up to 17 days. At the next time intervals tested (28 and 42 days), the CA frequency returned to the control level. In disagreement with these data obtained directly on metaphases, the MN frequency, as evaluated in polychromatic erythrocytes, decreased quickly after treatment, reaching the control value on the 5th day. We attempted to enhance the sensitivity of the MN test by using CREST antibodies and indirect immunofluorescence. However, higher proportions of CREST- MN in treated than in control animals were observed only at short time intervals, confirming the results obtained with the conventional MN assay.     

Comparative studies of monohemic bacterial C-type cytochromes. Redox and optical properties of Desulfovibrio desulfuricans Norway cytochrome C553(550) and Pseudomonas aeruginosa cytochrome C551

Redox properties of cytochrome c553(550) from Desulfovibrio desulfuricans Norway (Eo' = 0.04 + 0.02 V/NHE) and cytochrome c551 from P. aeruginosa (Eo = 0.25 +/- 0.02 V/NHE) are compared with those of some monohemic c-type cytochromes. The pK value for the equilibrium between the pH-dependent forms of cytochrome c553(550) (pK = 10.3 +/- 0.1) has been also determined. It is to be noted that the difference between redox potentials can extend to nearly 250 mV, though the axial heme ligands are identical. Structural reasons have to be invoked to explain these variations.     

Single-molecule insight into stalled replication fork rescue in Escherichia coli

DNA replication forks stall at least once per cell cycle in Escherichia coli. DNA replication must be restarted if the cell is to survive. Restart is a multi-step process requiring the sequential action of several proteins whose actions are dictated by the nature of the impediment to fork progression. When fork progress is impeded, the sequential actions of SSB, RecG and the RuvABC complex are required for rescue. In contrast, when a template discontinuity results in the forked DNA breaking apart, the actions of the RecBCD pathway enzymes are required to resurrect the fork so that replication can resume. In this review, we focus primarily on the significant insight gained from single-molecule studies of individual proteins, protein complexes, and also, partially reconstituted regression and RecBCD pathways. This insight is related to the bulk-phase biochemical data to provide a comprehensive review of each protein or protein complex as it relates to stalled DNA replication fork rescue.     

How short are we on the goal line of estimating insect-plant interaction in a hyperdiverse tropical environment?

Journal of Insect Conservation - In ecology, dealing with sample design is a constant challenge, especially in interaction networks, where most studies suffer from undersampling. Different sampling...     

Assessing environmental requirements effects on forest fragmentation sensitivity in two arboreal rodents

The study of the effect of habitat fragmentation on species that inhabit residual patches requires the investigation of the relationship existing between species distribution and landscape components. To understand which components of landscape mosaics are more influential for species’ persistence, we compared the distribution of two arboreal rodents proved to be sensitive to habitat fragmentation, the hazel dormouse Muscardinus avellanarius and the red squirrel Sciurus vulgaris. Their occurrence in residual oak woods in central Italy was studied with nest-boxes and hair-tubes, developing a new method for hair analysis. Their distributions were analysed considering patch, matrix composition and configuration, and landscape vegetation variables. The two species showed a different degree of plasticity, with the squirrel being significantly more specialised at the landscape scale. The comparison of the two distribution patterns highlighted the influence of different ecological constraints and the existence of different strategies to cope with fragmentation. Patch size and patch attributes were generally weaker determinants of occurrence, compared to landscape metrics. The squirrel presence was significantly influenced by the presence of shared perimeter between hedgerows and woods and by the lack of isolation of the residual patches, suggesting the use of several fragments to compensate the low habitat quality. Conversely the hazel dormouse seemed to be more affected by the internal management of the woods, and in particular by the mean DBH. Our results highlight how the recognition of the extrinsic constraints and the influence of multi-scale habitat selection may help guiding land use management, to ensure species conservation in profoundly exploited landscapes.     

De novo ABA synthesis and expression of seed dormancy in a gymnosperm: Pseudotsuga menziesii

Seeds of dormant Douglas-fir seeds germinated poorly when they were cultivated at 20–23 °C while isolated embryos germinated fully within two weeks. Seed dormancy was therefore imposed on the embryo by its surrounding structures. This physiological behaviour was well correlated with changes in ABA level during culture. Indeed, the ABA level decreased in isolated embryos while it increased in both embryo and megagametophyte during culture of whole seeds. The origin of this increase was analysed and the different ways by which seed coats could interfere with ABA accumulation are discussed.     

Hydrolysis of a chitosan-induced milk aggregate by pepsin, trypsin and pancreatic lipase.

The addition of chitosan to whole milk results in dose dependent destabilization and coagulation of the casein micelles and milk fat. The present study evaluates how the presence of chitosan could affect the hydrolysis of this chitosan-induced aggregate by different gastrointestinal proteases (pepsin and trypsin) and by pancreatic lipase. The chitosan-milk aggregate was hydrolyzed by pepsin and trypsin, as evaluated by the UV absorbance of TCA-soluble peptides and by urea-PAGE. The kinetics and extent of hydrolysis were independent of the casein being soluble or aggregated. The release of soluble peptides from the aggregate was independent of the presence of chitosan. A progressive inhibition of pancreatic lipase was observed in proportion to the increase in molecular weight of the chitosan employed to induce the formation of the aggregate. Interestingly, the presence of chitosan not only affected the initial velocity of the reaction, but also reduced its extent. The results indicate that a milk aggregate induced by chitosan was very well digested by gastric and intestinal proteases independently of the molecular weight of the chitosan used, and that the aggregate could retain the lipid-lowering effect of chitosan.