In an attempt to create the first comprehensive map of gene activity after death, an International team of scientists has found that the cells in human body continue to function even after an individual's death. During the study, the researchers analyzed various post-mortem samples, and the results indicated that some genes become more active after death.
This scientific study report is published in the journal Nature Communications.
During the research, Professor Roderic Guigó, at the Centre for Genomic Regulation in Spain and a crew comprised of scientists from the US and Europe examined 36 different types of tissue from 540 dead individuals and tried to determine the rise and fall of gene activities after death. Scientists noted that gene activity in body parts including muscles dropped off immediately soon after the blood circulation ceased.
But genes like HBA1 ramped up over time. The HBA1 gene is responsible for encoding a type of haemoglobin which shuttles oxygen all across the body. The gene activity of HBA1 consistently increased in colon and testis even after the death of the individual.
"There is a reaction by the cells to the death of the individual. We see some pathways, some genes, that are activated and this means that sometime after death there is still some activity at the level of transcription," said Professor Roderic Guigó, BBC reports.
However, the exact reason which increases the gene activity is still unknown. Professor Roderic Guigó believes that it might be the cessation of blood flow which results in the drop and rise of gene activities in the body of a person after death.
"I would guess that one of the major changes is due to the cessation of flow of blood, therefore I would say probably the main environmental change is hypoxia, the lack of oxygen, but I don't have the proof for this," added Roderic Guigó.
Scientists believe that understanding the changes in RNA levels will help contribute a lot to forensic investigations. The research team has also developed a software capable of analyzing the gene patterns to calculate how long since the person died.
"We conclude that there is a signature or a fingerprint in the pattern of gene expression after death that could eventually be used in forensic science, but we don't pretend we have now a method that can be used in the field," said Roderic Guigo.
Guigo also made it clear that new software needs some additional fine-tuning before it could be added to the forensic toolkit.
In a related development, in November a team of scientists from New York University Langone School of Medicine, investigated the phenomenon that dead people can hear their death being announced soon after as brain remains functional for some time. Their studies on people in Europe and the US, who suffered cardiac arrest but came back to life showed that there is evidence that proves that when someone who is dead, can actually hear their own death being announced by doctors.
In medical terms, death is defined based on when the heart stops beating, thus cutting off blood supply to the brain. A chain reaction is induced leading to a cellular process, killing brain cells one by one. However, this might take hours after the heart stops beating completely. A cardiopulmonary resuscitation (CPR) that was unsuccessful in reviving the patient, can still send around 15 percent blood to the brain that helps it to function normally for a while.
The brain, therefore, remains aware of the surroundings although it gradually keeps dying simultaneously, but at a slower rate. The person thus after being declared dead can hear and sense everything going on around him, they said.