Oxidative stress in brain during experimental bacterial meningitis: differential effects of alpha-phenyl-tert-butyl nitrone and N-acetylcysteine treatment

Antioxidant treatment has previously been shown to be neuroprotective in experimental bacterial meningitis. To obtain quantitative evidence for oxidative stress in this disease, we measured the major brain antioxidants ascorbate and reduced glutathione, and the lipid peroxidation endproduct malondialdehyde in the cortex of infant rats infected with Streptococcus pneumoniae. Cortical levels of the two antioxidants were markedly decreased 22 h after infection, when animals were severely ill. Total pyridine nucleotide levels in the cortex were unaltered, suggesting that the loss of the two antioxidants was not due to cell necrosis. Bacterial meningitis was accompanied by a moderate, significant increase in cortical malondialdehyde. While treatment with either of the antioxidants alpha-phenyl-tert-butyl nitrone or N-acetylcysteine significantly inhibited this increase, only the former attenuated the loss of endogenous antioxidants. Cerebrospinal fluid bacterial titer, nitrite and nitrate levels, and myeloperoxidase activity at 18 h after infection were unaffected by antioxidant treatment, suggesting that they acted by mechanisms other than modulation of inflammation. The results demonstrate that bacterial meningitis is accompanied by oxidative stress in the brain parenchyma. Furthermore, increased cortical lipid peroxidation does not appear to be the result of parenchymal oxidative stress, because it was prevented by NAC, which had no effect on the loss of brain antioxidants.

Sulfate and Nitrate Assimilation in Leaves of Quercus ilex and Quercus pubescens Grown Near Natural CO2 Springs in Central Italy

The effect of long-term exposure to elevated pCO2 concentrations on sulfate and nitrate assimilation was studied under field conditions using leaves from Quercus ilex and Quercus pubescens trees growing with ambient or elevated CO2 concentrations in the vicinity of three natural CO2 springs, Bossoleto, Laiatico and Sulfatara, in Tuscany, Italy. The activity of the key enzymes of sulfate assimilation, adenosine 5′-phosphosulfate reductase (APR) and nitrate assimilation, nitrate reductase (NR), were measured together with the levels of acid soluble thiols, and soluble non-proteinogenic nitrogen compounds. Whereas NR activity remained unaffected in Q. ilex or increased Q. pubescence, APR activity decreased in the area of CO2 springs. The latter changes were often accompanied by increased GSH concentrations, apparently synthesized from H2S and SO2 present in the gas mixture emitted from the CO2 springs. Thus, the diminished APR activity in leaves of Q. ilex and Q. pubescence from spring areas can best be explained by the exposure to gaseous sulfur compounds. Although the concentrations of H2S and SO2 in the gas mixture emitted from the vents at the CO2 springs were low at the Bossoleto and Laiatico spring, these sulfur gases pose physiological effects, which may override consequences of elevated pCO2.

In-situ, satellite measurement and model evidence on the dominant regional contribution to fine particulate matter levels in the Paris Megacity

A detailed characterization of air quality in the megacity of Paris (France) during two 1-month intensive campaigns and from additional 1-year observations revealed that about 70% of the urban background fine particulate matter (PM) is transported on average into the megacity from upwind regions. This dominant influence of regional sources was confirmed by in situ measurements during short intensive and longer-term campaigns, aerosol optical depth (AOD) measurements from ENVISAT, and modeling results from PMCAMx and CHIMERE chemistry transport models. While advection of sulfate is well documented for other megacities, there was surprisingly high contribution from long-range transport for both nitrate and organic aerosol. The origin of organic PM was investigated by comprehensive analysis of aerosol mass spectrometer (AMS), radiocarbon and tracer measurements during two intensive campaigns. Primary fossil fuel combustion emissions constituted less than 20%in winter and 40%in summer of carbonaceous fine PM, unexpectedly small for a megacity. Cooking activities and, during winter, residential wood burning are the major primary organic PM sources. This analysis suggests that the major part of secondary organic aerosol is of modern origin, i.e., from biogenic precursors and from wood burning. Black carbon concentrations are on the lower end of values encountered in megacities worldwide, but still represent an issue for air quality. These comparatively low air pollution levels are due to a combination of low emissions per inhabitant, flat terrain, and a meteorology that is in general not conducive to local pollution build-up. This revised picture of a megacity only being partially responsible for its own average and peak PM levels has important implications for air pollution regulation policies.

NO2-induced nitrate reductase activity in needles of Norway spruce (Picea abies) under laboratory and field conditions

The induction of activity of the enzyme nitrate reductase (NR, EC 1.6.6.1, 1.6.6.2) in needles of Norway spruce (Picea abies[L.] Karst.) by nitrogen dioxide (NO2) was studied under laboratory and field conditions. In fumigation chambers an increase in nitrate reductase activity (NRA) was detected 4 h after the start of the NO2 treatment. During the first 2 days with 100 µg NO2 m−3, NRA reached a constant level and did not change during the following 4 days. At the same level of NO2, NRA was lower in needles from trees grown on NPK-fertilized soil than on non-fertilized soil. After the transfer of spruce trees from fertilized soil to NPK-rich nutrient solution, NRA was transiently increased. This effect was assigned to root injuries causing nitrate transport to the shoot and subsequent induction of NRA. Neither trees on fertilized soil nor trees transferred to NPK-poor nutrient solution had increased NRA unless NO2 was provided. The NO2 gradient in the vicinity of a highway was used to test the long-term effect of elevated levels of NO2 on needle NRA of potted and field-grown spruce trees. Compared with less polluted sites, permanently increased NRAs were detected when NO2 concentrations were above 20 µg m−3. Controls of field measurements some 10 years after the introduction of catalytic converters in cars showed no significant change neither in NO2 levels nor in the decreasing NRA of spruce needles with the distance from the highway.