Obstructive parotitis from extraorally introduced foreign body in the Stensen duct.

A rare phenomenon, the extraoral traumatic penetration of a foreign body into the lumen of the parotid duct, is described. The ensuing obstructive symptomatology and its diagnostic approach and therapy are reviewed.

The diheme cytochrome c peroxidase from Shewanella oneidensis requires reductive activation.

We report the characterization of the diheme cytochrome c peroxidase (CcP) from Shewanella oneidensis (So) using UV-visible absorbance, electron paramagnetic resonance spectroscopy, and Michaelis-Menten kinetics. While sequence alignment with other bacterial diheme cytochrome c peroxidases suggests that So CcP may be active in the as-isolated state, we find that So CcP requires reductive activation for full activity, similar to the case for the canonical Pseudomonas type of bacterial CcP enzyme. Peroxide turnover initiated with oxidized So CcP shows a distinct lag phase, which we interpret as reductive activation in situ. A simple kinetic model is sufficient to recapitulate the lag-phase behavior of the progress curves and separate the contributions of reductive activation and peroxide turnover. The rates of catalysis and activation differ between MBP fusion and tag-free So CcP and also depend on the identity of the electron donor. Combined with Michaelis-Menten analysis, these data suggest that So CcP can accommodate electron donor binding in several possible orientations and that the presence of the MBP tag affects the availability of certain binding sites. To further investigate the structural basis of reductive activation in So CcP, we introduced mutations into two different regions of the protein that have been suggested to be important for reductive activation in homologous bacterial CcPs. Mutations in a flexible loop region neighboring the low-potential heme significantly increased the activation rate, confirming the importance of flexible loop regions of the protein in converting the inactive, as-isolated enzyme into the activated form.

Reflections on Darwin and Darwinizing.

Although there is a vast literature about Darwin there remains an urgent need, particularly in the field of literary studies, for greater understanding of his work. This essay examines current trends in Darwinian criticism, contrasting Literary Darwinism--which seeks in literature the "human nature" being defined by evolutionary psychology--with other models of Darwinian criticism provided by historians of science and literary scholars, models that bring together a sense of historical context with original attention to form and language. Such attention points toward future work that might alter our understanding of Darwin's achievement, both as scientist and writer, and thus change our sense of the affective implications of the world he represents.