A new approach to the assessment of regional myocardial blood flow and fractional oxygen extraction has been developed using 15O-water (H2-15O) and 15O-hemoglobin (15O-Hb). Bolus doses (1 mCi) of H2-15O and 15O-Hb were injected 10 minutes apart into the left main coronary artery of 12 normal dogs. Sequential images of regional myocardial tracer clearance were obtained over 5 minutes with a posi...

The production of hydrogen peroxide (H2 O2 ) drives tumourigenesis in ulcerative colitis (UC). Recently, we showed that H2 O2 activates DNA damage checkpoints in human colonic epithelial cells (HCEC) through c-Jun N-terminal Kinases (JNK) that induces p21(WAF1) . Moreover, caspases circumvented the G1/S and intra-S checkpoints, and cells accumulated in G2/M. The latter observation raised the qu...

BACKGROUND The mechanisms involved in reactive oxygen species and matrix metalloproteinase (MMP)-mediated periodontal tissue breakdown are unknown. OBJECTIVE To determine the effect of H2 O2 in MMP-2 and MMP-9 activity, and the involvement of nuclear factor kappa B (NFκB) and Ca(2+) -mediated signals in human periodontal ligament fibroblasts. MATERIAL AND METHODS Primary cultures were chara...

BACKGROUND FeFe-hydrogenases are the most active class of H2-producing enzymes known in nature and may have important applications in clean H2 energy production. Many potential uses are currently complicated by a crucial weakness: the active sites of all known FeFe-hydrogenases are irreversibly inactivated by O2. RESULTS We have developed a synthetic metabolic pathway in E. coli that links Fe...

An oxygen-tolerant respiratory [NiFe]-hydrogenase is proven to be a four-electron hydrogen/oxygen oxidoreductase, catalyzing the reaction 2 H2 + O2 = 2 H2O, equivalent to hydrogen combustion, over a sustained period without inactivating. At least 86% of the H2O produced by Escherichia coli hydrogenase-1 exposed to a mixture of 90% H2 and 10% O2 is accounted for by a direct four-electron pathway...

We have been investigating the use of organic pigments as semiconductor photocatalysts in a dual stage water decomposition scheme that would ultimately use solar energy to generate hydrogen from water. We have shown that by employing a combination of simple screening procedures on prospective compounds, such as semiempirical molecular orbital calculations and thin film voltammetry, we can quick...

BACKGROUND Under low O2 concentration (hypoxia) and low light, Chlamydomonas cells can produce H2 gas in nutrient-replete conditions. This process is hindered by the presence of O2, which inactivates the [FeFe]-hydrogenase enzyme responsible for H2 gas production shifting algal cultures back to normal growth. The main pathways accounting for H2 production in hypoxia are not entirely understood,...

It is widely accepted that photosynthetic bacteria played a crucial role in Fe(II) oxidation and the precipitation of iron formations (IF) during the Late Archean-Early Paleoproterozoic (2.7-2.4 Ga). It is less clear whether microbes similarly caused the deposition of the oldest IF at ca. 3.8 Ga, which would imply photosynthesis having already evolved by that time. Abiological alternatives, suc...