Pawan Kushwaha

Publications (36) View all

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  Available from: Pawan Kushwaha

  Article: Thoracolumbar burst fractures treated with posterior decompression and pedicle screw instrumentation supplemented with balloon-assisted vertebroplasty and calcium phosphate reconstruction. Surgical technique.

  Rex A W Marco, B Christoph Meyer, Vivek P Kushwaha
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  ABSTRACT: The treatment of unstable thoracolumbar burst fractures with short-segment posterior spinal instrumentation without anterior column reconstruction is associated with a high rate of screw breakage and progressive loss of reduction. The purpose of the present study was to evaluate the functional, neurologic, and radiographic results following transpedicular, balloon-assisted fracture reduction with anterior column reconstruction with use of calcium phosphate bone cement combined with short-segment posterior instrumentation and a laminectomy. A consecutive series of thirty-eight patients with an unstable thoracolumbar burst fracture with or without neurologic deficit were managed with transpedicular, balloon-assisted fracture reduction, calcium phosphate bone cement reconstruction, and short-segment spinal instrumentation from 2002 to 2005. Twenty-eight of the thirty-eight patients were followed for a minimum of two years. Demographic data, neurologic function, segmental kyphosis, the fracture severity score, canal compromise, the Short Form-36 score, the Oswestry Disability Index score, and treatment-related complications were evaluated prospectively. All thirteen patients with incomplete neurologic deficits had improvement by at least one Frankel grade. The mean kyphotic angulation improved from 17 degrees preoperatively to 7 degrees at the time of the latest follow-up, and the loss of vertebral body height improved from a mean of 42% preoperatively to 14% at the time of the latest follow-up. Screw breakage occurred in two patients, and pseudarthrosis occurred in one patient. The present study demonstrates that excellent reduction of unstable thoracolumbar burst fractures with and without associated neurologic deficits can be maintained with use of short-segment instrumentation and a transpedicular balloon-assisted reduction combined with anterior column reconstruction with calcium phosphate bone cement performed through a single posterior incision. The resultant circumferential stabilization combined with a decompressive laminectomy led to maintained or improved neurologic function in all patients with neurologic deficits, with a low rate of instrumentation failure and loss of correction.
  The Journal of Bone and Joint Surgery 03/2010; 92 Suppl 1 Pt 1:67-76. · 3.27 Impact Factor
• Article: Reaction of hypochlorous acid with imidazole: formation of 2-chloro- and 2-oxoimidazoles.

  N R Jena, P S Kushwaha, P C Mishra
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  ABSTRACT: Reaction of hypochlorous acid (HOCl) with imidazole (Im) taken as a model for the 5-membered ring of guanine, leading to the products 2-chloro- and 2-oxo-imidazoles was investigated at the B3LYP/6-31+G* and B3LYP/AUG-cc-pVDZ levels of density functional theory. For all cases, single point energy calculations were performed at the MP2/AUG-cc-pVDZ level of theory using the geometries optimised at the B3LYP/AUG-cc-pVDZ level. Intrinsic reaction coordinate calculations were performed to ensure genuineness of all the calculated transition states. Effect of aqueous media was investigated by solvating all the species involved in the reactions using the polarizable continuum model. It is found that 2-chloroimidazole (2-ClIm) can be formed following three different reaction schemes while 2-oxoimidazole (2-oxoIm) can be formed following two different reaction schemes. The calculated barrier energies show that formation of 2-oxoIm would be less favored than that of 2-ClIm, which explains the experimental observations on relative yields of 8-chlorodeoxyguanosine and 8-oxodeoxyguanosine.
  Journal of Computational Chemistry 02/2008; 29(1):98-107. · 4.58 Impact Factor
• Article: Electronic transitions of guanine tautomers, their stacked dimers, trimers and sodium complexes.

  P S Kushwaha, Anil Kumar, P C Mishra
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  ABSTRACT: Planar and nonplanar geometries of the keto-N9H and keto-N7H tautomers of the guanine base of DNA as well as the hydrogen bonded complexes of these species with three water molecules each were optimized using the density functional theory at the B3LYP/6-31G** level. Geometries of the isolated bases were also optimized using the ab initio approach at the MP2/6-31G** level. The isolated keto-N9H and keto-N7H tautomers as well as their hydrogen bonded complexes with three water molecules each were solvated in bulk water employing the polarized continuum model (PCM) of the self-consistent reaction field theory (SCRF). Stacked dimers and trimers of both the tautomers of guanine were generated by placing the planar forms of the species at a fixed distance of 3.5 A from the neighboring one and rotating one molecule with respect to the other by 110 degrees for the keto-N9H form and 90 degrees for the keto-N7H form which corresponded to total energy minima at the B3LYP/6-31G** level. Geometry optimization for the cation of the monomer of guanine was performed at the same level of theory, and its solvation in bulk water was treated using the PCM model of the SCRF theory. The geometries of complexes of the two tautomers of guanine with a Na+ ion each were optimized at the B3LYP/6-31G** level, and the Na+ ion is predicted to bind with the keto-N9H tautomer preferentially. While the complex of the keto-N7H form of guanine with three water molecules in gas phase is slightly more stable than the corresponding complex of the keto-N9H form of guanine, the reverse is true in bulk water. Stacking interactions enhance the relative stability of the keto-N9H tautomer over that of the keto-N7H tautomer, suggesting that in bulk solutions, the former would be dominant. Electronic spectra of the isolated tautomers of guanine, those of their complexes with three water molecules each, the (keto-n9h and keto-n7h) cation of guanine, the complexes of the tautomers with a Na+ ion each, the stacked dimers and trimers of the two tautomers were calculated using configuration interaction involving single electron excitations (CIS). The relative absorption intensities of the two tautomers of guanine near 275 and 248 nm in the monomer, dimer, and trimer are predicated to be in the opposite order. Thus the absorption intensity oscillation observed using a guanine aqueous solution can be explained in terms of oscillation of relative populations of the two tautomers of the molecule. The 248 nm absorption peak would be appreciably red-shifted on formation of the cation of guanine. Binding of the Na+ ion with the two tautomers of guanine reduces intensities of their transitions appreciably and also it causes large red-shifts in the same.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 03/2004; 60(3):719-28. · 2.10 Impact Factor
• Article: A geometry optimization and molecular electrostatic potential mapping study of structure-activity relationship for some anti-Alzheimer agents.

  P S Kushwaha, M K Shukla, P C Mishra
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  ABSTRACT: Molecular geometries of some substituted (pyrroloamino)pyridines which possess anti-Alzheimer activity were optimized and potential-derived CHelpG point charges were computed using ab initio SCF molecular orbital approach employing the 3-21G basis set. AM1 molecular orbital calculations were performed using these optimized geometries and thus optimized Hybridization. Displacement Charges (HDC) combined with Löwdin charges continuously distributed in three dimension were obtained. Molecular electrostatic potential (MEP) maps of the molecules were obtained in two ways: (i) using the HDC-based model with the help of which MEP minima near the molecules were located, and (ii) using the CHelpG point charges, MEP values on the van der Waals surfaces of the molecules were computed. The MEP maps computed using both the methods have negative MEP regions near the pyridine nitrogen atom which appears to be the main binding site of the molecules with the appropriate receptor. Both electrostatic interaction and lipophilic association between these molecules and the receptor appear to contribute to biological activity.
  Indian journal of biochemistry & biophysics 05/1999; 36(2):101-6. · 1.14 Impact Factor
• Article: Performance characteristics of a rapid diagnostic test for malaria, when used to confirm cerebral malaria in children and young adults.

  V Venkatesh, P K Patibandla, G G Agarwal, S Awasthi, R C Ahuja, V L Nag, K P Kushwaha, S K Agarwal
  Annals of Tropical Medicine and Parasitology 02/2007; 101(1):85-7. · 1.43 Impact Factor