Biomedical subjects

R Majumdar

Publications and source records attributed to R Majumdar.

38 records · Page 3Linked to original sources

PubMedDate not supplied

Evidence of two mechanisms of prostaglandin release in an in vitro model of muscle damage. Possible therapeutic implications.

In spite of recent progress, treatment of muscle disease based on specific gene therapy is not yet available. An alternative approach is to develop treatment which affords non-specific protection against general factors involved in cell damage. This approach is used effectively to prevent neuronal damage in experimental brain ischemia in animals and has been proposed for human trials. The most effective intervention is the use of mild (35 degrees C) hypothermia. An in vitro model to study muscle cell damage employs the rat epitrochlearis muscle exposed to low concentrations of 2:4-dinitrophenol, an uncoupler of oxidative phosphorylation. The efflux of prostaglandin E2 (PGE2) from the muscle is used as an indicator of muscle damage. We now show that there are two types of PGE2 release. "Basal" efflux gradually declines with decreasing temperatures and is not affected by removal of calcium from the medium. The efflux of PGE2 in response to metabolic stress is dependent on the presence of calcium and is abolished by mild hypothermia of 35 degrees C. The latter effect suggests that cell death is muscle and neurons have features in common and that muscle may be a useful tissue in which to investigate this phenomenon further.

Adenosine Triphosphate↗

PubMedDate not supplied

Structural basis of DNA flexibility.

It has been recently shown by us, on the basis of crystal structure database that the flexibility of B-DNA double helices depends significantly on their base sequence. Our model building studies further indicated that the existence of bifurcated cross-strand hydrogen bonds between successive base pairs is possibly the main factor behind the sequence directed DNA flexibility. These cross-strand hydrogen bonds are, of course, weaker than the usual Watson-Crick hydrogen bonds and their bond geometry is characterized by relatively larger bond lengths and smaller bond angles. We have tried to improve our model structures by incorporating non-planarity of the amino groups in DNA bases due to the presence of lone pair electrons at the nitrogen atoms. Energy minimization studies have been carried out by using different quantum chemical methods, whereby it is found that in all cases of N-H....O type cross-strand hydrogen bonds, the bond geometry improves significantly. In the cases of N-H....N type hydrogen bonds, however, no such consistent improvements can be noticed. Perhaps the true picture would emerge only if all the other interactions present in the DNA macromolecule could be appropriately taken into account.

Crystallography↗