RESUMEN
OBJECTIVE: Death due to burn occurs frequently. This study investigated time-dependent alterations in cardiac troponin T (cTnT) associated with fatal burns. METHODS: Cardiac tissue samples were collected from 10 medico-legal autopsies after informed consent from the relatives and post-mortem degradation by incubation of the cardiac tissue was studied at room temperature for different time periods. The cases included in this study were the subjects of burns without any prior history of disease who died in the hospital and their exact time of death was known. An efficient extraction protocol to analyse the banding pattern of cTnT in post-mortem tissue was developed. RESULTS: The data show a distinct time-dependent profile corresponding to the degradation of cTnT by proteases found in cardiac muscle. Both post-mortem interval and cardiac tissue of burned corpses had a statistically significant effect where the greatest amount of protein breakdown was observed within the first 41.20 hours, after which intact protein slowly disappears. The average molecular weight of all fragments showed intact cTnT to be rapidly degraded into smaller fragments. CONCLUSION: In cases of burns, such knowledge will assist in knowing if there were previous scars that might have mimicked a burn and also help to properly evaluate the real cause of death.
RESUMEN
A cDNA encoding a plasma membrane Ca2+ pump mutant V674P(ct120) was constructed and expressed in COS-1 cells. Immunoblots of transfected COS-1 membranes showed that the V674P(ct120) and the wild-type hPMCA4b(ct120) proteins were expressed at similar levels. The change of Val674 to Pro reduced the activity of the hPMCA4b(ct120) to an extent similar to that observed previously in the full-length Ca2+ pump (Adamo et al. (1995) J. Biol. Chem. 270, 30111-30114). Despite its lower activity, the apparent affinity for Ca2+ of the V674P(ct120) enzyme was at least as high as that of hPMCA4b(ct120), indicating that substitution of Val674 by Pro did not impair the interaction of the enzyme with Ca2+. The sensitivity of the V674P(ct120) enzyme to inhibition by vanadate was not significantly different from that of the hPMCA4b(ct120), supporting the idea that the mutation did not alter the equilibrium between E2-E1. The study of the Mg2+ dependency of the Ca2+ transport showed that the V674P(ct120) mutant reached maximum activation at 100 microM Mg2+ in contrast with 500 microM in the hPMCA4b(ct120). Furthermore, while at 2 mM Mg2+ the hPMCA4b(ct120) showed no sign of inhibition, the activity of the mutant decreased to less than 50% of the maximum activity observed at 100 microM Mg2+. These results indicate that the decrease in the activity observed upon substitution of Val674 by Pro was due to a higher sensitivity to Mg2+ as inhibitor.