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Biomedical subjects

B Sridhar

Publications and source records attributed to B Sridhar.

12 recordsLinked to original sources
PubMed2006

Donepezilium oxalate trihydrate, a therapeutic agent for Alzheimer's disease.

Donepezil, a cholinesterase inhibitor with good central nervous system penetration, has been crystallized as a tertiary amine salt with a disordered oxalate anion to give the title compound, (R,S)-1-benzyl-4-[(5,6-dimethoxy-1-oxoindan-2-yl)methyl]piperidinium hydrogen oxalate trihydrate, C24H30NO3+.C2HO4-.3H2O. The indanone and piperidine ring planes are inclined at an angle of 33.4 (1) degrees. A comparison is made with the piperidinium cation bound in acetylcholinesterase in the solid state. The methylene units bridging the indanone-piperidine-benzyl groups determine the molecular shape and conformational features. The structure is stabilized mainly by O-H...O and N-H...O hydrogen bonds, with water molecules mediating interactions between oxalate anions and donepezilium cations.

Alzheimer Disease↗
PubMed2006

Dimorphism in (2Z)-2-benzylidene-N,7-dimethyl-3-oxo-5-phenyl-2,3-dihydro-5H-1,3-thiazolo[3,2-a]pyrimidine-6-carboxamide.

The title compound, C22H19N3O2S, crystallizes in two polymorphic forms having the same space group, viz. P-1, with Z' = 2 and Z' = 1. In both polymorphs, the planar thiazole ring is fused cis with the dihydropyrimidine ring, the carbamoyl group is in an extended conformation with an anticlinal orientation with respect to the pyrimidine ring, and the phenyl ring is attached to the pyrimidine ring approximately at a right angle. The two polymorphs have different interplanar angles between the phenyl and thiazole rings. The molecules are linked by N-H...O and C-H...O hydrogen bonds.

Journal Article↗
PubMed2006

Imino Diels-Alder adducts. XII. Two pyrano[3,2-c]quinolines.

The crystal structures of pyranoquinolines 9-fluoro-5-phenyl-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c]quinoline, C18H18FNO, and 9-methyl-5-phenyl-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c]quinoline, C19H21NO, are isomorphous. In both structures, the pyran ring is exo to the six-membered N-heterocyclic ring formed in the cycloaddition step. The torsion angles across the phenyl linkage for the two structures are -91.2 (1) and -88.3 (2) degrees. The striking feature in both crystal packings is that they do not contain the expected conventional hydrogen bonds, in spite of the presence of good hydrogen-bonding functionalities. Possible C-H...pi interactions are, however, observed.

Crystallography, X-Ray↗
PubMed2005

Imino Diels-Alder adducts. II. Two pyrano[3,2-c]quinolines.

8-Chloro-9-fluoro-5-phenyl-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c]quinoline and 10-chloro-9-fluoro-5-phenyl-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c]quinoline, both C18H17ClFNO, are diastereoisomers, formed as the result of the imino Diels-Alder reactions of N-benzylideneanilines with 3,4-dihydro-2H-pyran. The crystal structures reveal the stereochemistry of the pyran ring, which is endo/exo to the quinoline ring system formed in the cycloaddition step. In both structures, the pyran ring adopts a chair conformation, while the nitrogen-containing heterocyclic ring prefers a half-chair conformation. The structures differ essentially in the relative orientation of the ring junction H atoms.

Crystallography, X-Ray↗
PubMed2004

Two carbamoyl-substituted dihydropyrimidines: potential mimics of dihydropyridine calcium channel blockers.

The structures of two conformationally similar 1,4-dihydropyrimidines with a novel carbamoyl substitution, viz. 6-methyl-5-(N-methylcarbamoyl)-4-phenyl-1,2,3,4-tetrahydropyrimidine-2-thione monohydrate, C13H15N3OS.H2O, (I), and 4-(4-chlorophenyl)-6-methyl-5-(N-methylcarbamoyl)-1,2,3,4-tetrahydropyrimidine-2-thione monohydrate, C13H14ClN3OS.H2O, (II), exhibit the structural features of 1,4-dihydropyridine calcium channel blockers. In both structures, the pyrimidine ring adopts a flattened boat conformation and the carbamoyl side chain is in an extended conformation with an anticlinal orientation. The phenyl ring occupies a pseudo-axial position with respect to the pyrimidine ring in these structures. Both compounds crystallize with one molecule of water, which participates in a two-dimensional hydrogen-bonding network. The molecules are linked into dimers by N-H...S hydrogen bonds in both structures.

Biomimetic Materials↗
PubMed1989

Long incomplete longitudinal fractures of the third metacarpal and metatarsal bone in horses.

Five horses with long incomplete longitudinal fractures of the third metacarpal bone and three horses with similar fractures of the third metatarsal bone were examined. In three of the metacarpal fractures a long incomplete fissure extended proximomedially, in association with the more common lateral condylar fracture of the third metacarpal bone, and in the other two cases the fracture originated from the medial aspect of the distal articular surface. In the three horses with fractures of the third metatarsal bone the fractures had a consistent spiral configuration.

Animals↗
PubMed1988

The management of bovine fractures: a review of 59 cases.

Current trends in bovine fracture repair are reviewed with reference to 59 cases. Thirty-one cases were managed surgically, 14 by external fixation, and six by stall confinement. Eight animals were slaughtered without treatment being attempted. A successful outcome was achieved in 90 per cent of the surgically treated cases, compared with 57 per cent for those treated by external fixation methods.

Animals↗
PubMed1980

On the feasibility of densitometric assessment of cerebral aneurysms.

Computer-aided operator-interactive densitometry was used to study the feasibility of quantitating the radiographic images of cerebral aneurysms. Contrast-filled tubings of varying diameter were used to investigate the linearity of the system and to assess the general accuracy and reproducibility of the densitometric method. To study the reproducibility of the technique on aneurysms, a vein pouch aneurysm model was developed in rabbits. Inter- and intra-operator errors were determined by four observers, who performed multiple measurements on various projections of aneurysm images taken both in vitro and in vivo. These errors ranged between 3 and 8% for the in vitro data, and 7 and 22% for the in vivo data. It was found that the current approach that utilizes the linear segment of the film-screen characteristic curve has to be extended to involve the non-linear segment at the 'toe' section of the characteristic curve for future clinical applications.

Absorptiometry, Photon↗
PubMed1979

Remote densitometric analysis of stenotic lesions.

In conventional densitometric evaluation of stenoses the digitized angiogram is displayed on a multi-grey-level scope to facilitate operator interaction. With a remote terminal, linked to the computer with regular telephone lines, such display is unacceptably slow. To circumvent this difficulty, the projection of the original image is used for interactions through a sonic pen digitizer interfaced to the computer. A coordinate system can be defined on the projected image, in addition to the blood vessel segment to be analyzed by the operator. The computer can retrieve these features on the stored-pre-digitized image to carry out the quantitative evaluation of the stenosis. This method reduces the time of analysis and allows several institutions to share the same computing facility.

Absorptiometry, Photon↗