Pitfalls in Cytodiagnosis of Pleomorphic Adenoma of the Nasal Septum - A Rare Case Report

Pleomorphic adenoma is the most common benign mixed tumor of major salivary gland. Ectopic occurrence of pleomorphic adenoma are seen in minor salivary glands of pharynx, trachea, larynx and very rarely in nasal septum. We report a case of 40 year old female who presented with right sided nasal mass and mild nasal obstruction since six months. Cytologically a possibility of pleomorphic adenoma was made which was confirmed by histopathological study. We present this case due to 1) rarity in the nasal septum 2) pitfalls at cytology due to abundance (predominance) of myoepithelial cells and scanty or even absent mesenchymal component and 3) under reporting in English literature to the best of our knowledge

Structural analysis of outer membrane beta-stranded porins using B-factor

Computational and statistical analysis has formed a large component of the biophysical efforts put forth to understand protein structure and function, due to the diversity and complexity of their structure. Outer membrane proteins form a diverse and complex set of proteins. Of these, porins that allow passage of molecules across the membrane interface have been analyzed here from a biophysical and structural perspective. The objective of this study is to analyze the structural organization of porins using atomic temperature factor as a parameter. Generally atomic temperature factors of molecules from crystal structures indicate the degree of mobility or disorder seen in the crystal structure. As good crystal structures have lesser possibilities of errors so there is lesser chance that errors are playing roles in temperature factors. Structures of six porins (four 16-stranded beta barrel porins and two 8-stranded beta barrel porins) were taken from the PDB for the analysis based on resolution and R-factor. Programs and scripts were written for extracting the temperature factors for the beta strands, loops and turns so that the analysis could be done for different atom-types and residue-types. The residue distribution and mobility distribution was found to be characteristic of each of the porins. The mobility and residue distribution amongst the secondary structural elements were found to follow the level of homology at the sequence and structural level. The loops that had defined functional roles in structural terms were found to have lower temperature factors than the other loops. The turn regions that are thought to face the periplasmic region in the cell, showed higher temperature factors. For both the 16 stranded and the 8-stranded barrels it was found one part of the barrel (the lower wall or 'inner' wall comprising the trimer interface in the case of the 16-stranded barrels) was more rigid and the other half of the barrel (the higher or 'outer' wall) showed more mobility as seen from the temperature factors. This seems to be an intrinsic structural component of the beta barrels

Accurate Evaluation of Charge Asymmetry in Aqueous Solvation

Charge hydration asymmetry (CHA)--a characteristic dependence of hydration free energy on the sign of the solute charge--quantifies the asymmetric response of water to electric field at microscopic level. Accurate estimates of CHA are critical for understanding hydration effects ubiquitous in chemistry and biology. However, measuring hydration energies of charged species is fraught with significant difficulties, which lead to unacceptably large (up to 300%) variation in the available estimates of the CHA effect. We circumvent these difficulties by developing a framework which allows us to extract and accurately estimate the intrinsic propensity of water to exhibit CHA from accurate experimental hydration free energies of neutral polar molecules. Specifically, from a set of 504 small molecules we identify two pairs that are analogous, with respect to CHA, to the K+/F- pair--a classical probe for the effect. We use these "CHA-conjugate" molecule pairs to quantify the intrinsic charge-asymmetric response of water to the microscopic charge perturbations: the asymmetry of the response is strong, ~50% of the average hydration free energy of these molecules. The ability of widely used classical water models to predict hydration energies of small molecules correlates with their ability to predict CHA