Hepatic elemental contents and antioxidant enzyme activities in Algerian mice (Mus spretus) inhabiting a mine area in central Portugal.

In this study the effects of heavy metals (manganese, iron, copper, zinc) and selenium exposure on the hepatic activity of antioxidant enzymes, superoxide dismutase (SOD) and glutathione S-transferases (GST), were appraised on a seasonal basis in Algerian mice (Mus spretus) inhabiting an active copper mine area. A reference population of the same species was considered for comparative purposes. Different patterns of seasonal variation were found in both populations for the manganese, iron and selenium hepatic concentrations and SOD activity. When the two populations were compared, iron and selenium concentrations were enhanced in mice from the polluted area. In addition, SOD activity was significantly decreased in summer in exposed mice, but no other significant changes in SOD and GST activities between sites throughout the year were recorded. However, when seasonal data within each group of mice were pooled, significant differences were found between sites for the average concentrations of manganese, iron and selenium, which are higher in the polluted site. In addition, significant differences were obtained for the average values of SOD and of GST activities, due to simultaneously higher GST values and slightly lower SOD values in the polluted site. The population from the reference site was more homogeneous for all parameters measured than the population from the polluted area. These results, in particular the higher variability in data collected from mice exposed to heavy metals and selenium, combined with the negative associations between biochemical markers and heavy metals, may suggest, despite the good adaptability of the mice to their habitat, biochemical stress due to diminished environmental quality.

Effect of base composition on DNA bending by phosphate neutralization.

Of the many forces involved in DNA bending by proteins, we have focused on the possible role of asymmetric phosphate neutralization due to interactions between the negatively charged phosphate backbone of duplex DNA and cationic amino acids of an approaching protein. The resulting unbalanced charge distribution along the duplex DNA is thought to induce the double helix to collapse toward the neutralized surface. Previous work has confirmed that DNA bending (approximately 20.7 +/- 4 degrees) is induced by asymmetric incorporation of six uncharged racemic methylphosphonate analogs partially neutralizing one face of GC-rich duplex DNA. We have now analyzed DNA duplexes with similar patches of methylphosphonate linkages in an AT-rich sequence context and again observe bending toward the neutralized face, to an extent (20 +/- 0.6 degrees) comparable to that observed for neutral patches in GC-rich DNA. The similar induced bend angles in AT-rich and GC-rich contexts does not reveal increased flexibility in AT-rich sequences, or a particular propensity of A-T base pairs to roll toward the minor groove in the tested sequences.