All living beings emit a strange glow linked to vitality that vanishes when they die, according to a study that may lead to a powerful new tool for medical diagnosis.
Life forms are essentially complex biochemical labs in which metabolism fuels life-sustaining processes.
A byproduct of this metabolism is a group of highly reactive oxygen-containing molecules called reactive oxygen species, or ROS.
Excess ROS production may lead to what is known as oxidative stress, which induces electron transfer processes between chemicals in the body linked to the glow, researchers from the University of Calgary in Canada said.
The study, published in The Journal of Physical Chemistry Letters, documents the strange glow called ultraweak photon emission, or UPE or biophoton emission, in mice.
Researchers found that live mice emitted significantly higher UPE with greater intensity, compared to recently dead mice.
In comparison, UPE varied in plants depending on exposure to stress factors like temperature changes, injury and chemical treatments.
Previous studies suggest ROS could be key to this glow, characterised by a spontaneous release of extremely low-intensity light invisible to the human eye.
The faint light falls in the spectral range of 200 to 1,000 nanometres and is observed across life forms, from single-celled organisms and bacteria to plants, animals and even humans.
But not much is known about the effect of mortality and stress on UPE.
The latest study compared this glow in living versus dead animals while visualising the effects of temperature, injury and chemical treatments on UPE in plants.
Scientists developed dark enclosures to eliminate environmental light interference and used special camera systems for imaging plants and animals.
They found that live mice showed robust light emissions while the faint glow from euthanised mice was nearly extinguished, despite both groups having the same body temperature of 37C.
“Our investigation reveals a significant contrast between the UPE from live vs dead mice,” scientists noted in the study.
“In plants, we observed that an increase in the temperature and injuries both caused an increase in UPE intensity.”
Chemical treatments also modified the glow characteristics of plants.
The application of a local anaesthetic – benzocaine – to the site of injury in plants led to the highest emission among the compounds tested, researchers noted.
The findings reveal that UPE can be a sensitive indicator of vitality in animals and of stress response in plants.
Scientists hope the study helps develop UPE imaging for future research and clinical diagnostics. “UPE imaging provides the possibility of non-invasive label-free imaging of vitality in animals and the responses of plants to stress,” they said.
