Accumulating evidence suggests that human parturition represents an inflammatory process. Leukocytes are known to infiltrate uterine tissues but the exact timing, nature and quantity of these cells has not been formally characterized. We have previously demonstrated an apparent increase in pro-inflammatory cytokines within tissues of the labouring uterus. The aims of this study were to quantify and compare the leukocyte subpopulations before and during labour in fetal membranes, decidua and cervix and to quantify and compare mRNA expression of interleukin-1beta (IL-1beta), IL-6, IL-8 and tumour necrosis factor-alpha in myometrium, cervix, chorio-decidua and amnion. Biopsies of each of these tissues were obtained from pregnant women delivered by Caesarean section before and after the onset of spontaneous labour at term. Subpopulations of leukocytes were identified using immunohistochemistry and cytokine mRNA expression was quantified using Northern analysis. We found that parturition was associated with a significant increase in IL-1beta, IL-6 and IL-8 mRNA expression in cervix and myometrium, IL-6 and IL-8 mRNA expression in chorio-decidua and IL-1beta and IL-8 mRNA expression in amnion. Histological analysis demonstrated that leukocytes (predominantly neutrophils and macrophages) infiltrate the uterine cervix coincident with the onset of labour. These data lend further support to the hypothesis that labour is an inflammatory process.

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The crystal structure and spectroscopic properties of the periplasmic penta-heme cytochrome c nitrite reductase (NrfA) of Escherichia coli are presented. The structure is the first for a member of the NrfA subgroup that utilize a soluble penta-heme cytochrome, NrfB, as a redox partner. Comparison to the structures of Wolinella succinogenes NrfA and Sulfospirillum deleyianum NrfA, which accept electrons from a membrane-anchored tetra-heme cytochrome (NrfH), reveals notable differences in the protein surface around heme 2, which may be the docking site for the redox partner. The structure shows that four of the NrfA hemes (hemes 2-5) have bis-histidine axial heme-Fe ligation. The catalytic heme-Fe (heme 1) has a lysine distal ligand and an oxygen atom proximal ligand. Analysis of NrfA in solution by magnetic circular dichroism (MCD) suggested that the oxygen ligand arose from water. Electron paramagnetic resonance (EPR) spectra were collected from electrochemically poised NrfA samples. Broad perpendicular mode signals at g similar 10.8 and 3.5, characteristic of weakly spin-coupled S = 5/2, S = 1/2 paramagnets, titrated with E(m) = -107 mV. A possible origin for these are the active site Lys-OH(2) coordinated heme (heme 1) and a nearby bis-His coordinated heme (heme 3). A rhombic heme Fe(III) EPR signal at g(z) = 2.91, g(y) = 2.3, g(x) = 1.5 titrated with E(m) = -37 mV and is likely to arise from bis-His coordinated heme (heme 2) in which the interplanar angle of the imidazole rings is 21.2. The final two bis-His coordinated hemes (hemes 4 and 5) have imidazole interplanar angles of 64.4 and 71.8. Either, or both, of these hemes could give rise to a "Large g max" EPR signal at g(z)() = 3.17 that titrated at potentials between -250 and -400 mV. Previous spectroscopic studies on NrfA from a number of bacterial species are considered in the light of the structure-based spectro-potentiometric analysis presented for the E. coli NrfA.