Biological agents do have some good uses
Poisoning one’s enemies is scarcely original – thousands of venomous species use the same tactic
We are electricity incarnate. Every move we make, every thought we have, every note we hear, the fleeting scent of a rose, every heartbeat and bowel contraction is powered by an electric current. The corollary, as we have recently been forcibly reminded by the fate of Sergei Skripal and his daughter Yulia, is that the most certain method of poisoning one’s enemies is to disrupt the body’s electric circuitry.
This is scarcely an original idea. For tens of millions of years, snakes, spiders, snails and squid and thousands of other venomous species have deployed the same tactic to incapacitate their prey and defend themselves against their foes. There are many ways of doing so, but the most vulnerable site of attack is the neuromuscular junction, where the chemical acetylcholine (ACH) is released from the nerve endings to initiate a muscular contraction.
Here, there are two options, the first – favoured, for example, by the black mamba and king cobra
– is to immobilise their prey by preventing the release of ACH, or blocking the receptor on which it acts. This results in a state of flaccid paralysis of the muscles and, no longer able to breathe, the victim dies from asphyxiation. The second, favoured by the rattlesnake and the Russian secret police, is to inactivate the enzyme that breaks down the acetylcholine molecules once they have fulfilled their purpose. This has the reverse effect, making the bodily functions go into overdrive – sweating, vomiting, frothing at the mouth, convulsions – until the muscles can contract no more, leading to death from exhaustion.
For all that, the benefits of biological agents that block the action of acetylcholine at the neuromuscular junction far outweigh the harms. The neurotoxin curare has made surgery vastly safer, as paralysing the muscles during an operation (while maintaining respiration on a ventilator) obviates the need for inducing a state of deep anaesthesia with a hefty dose of barbiturates or nitrous oxide.
Then there is the most potent of all poisons, botulinum toxin, from the bacterium Clostridium – a couple of kilograms being sufficient to annihilate the entire human race. But its paralysing effects when injected in minuscule amounts in the form of Botox has transformed the treatment of more than 20 medical conditions, including strabismus, spasticity following a stroke, an overactive bladder and the muscular spasms of dystonia.
Eye-watering pain
This week’s medical query comes courtesy of Mrs TM from Leeds, in her mid-seventies, who for the past couple of years has suffered periodic bouts of excruciating pain and watering of either the left or right eye – but never both simultaneously.
The episodes begin with a feeling of pressure behind the eyeball, gradually increasing in intensity before she has to take to her bed, preferably in a darkened room. Even then, the slightest movement of her eyes, such as looking down at her wristwatch, and “the top of my head nearly comes off ”.
She has a high pain threshold (four children, a knee replacement and other operations), but cannot get through these attacks without a hefty dose of cocodamol. Numerous medical consultations, visits to A&E and a panoply of the usual investigations have ruled out sinusitis, temporal arteritis, brain tumours and other possible diagnoses. She would be immensely grateful to hear from anyone similarly afflicted.
Water allergy solved
Finally, a “very fit” 87-year-old writes to say that after 27 years living in the same house in Cambridgeshire, she has become allergic to the local tap water. She is fine when visiting friends in Tewkesbury and Hampshire, but back home, her skin reddens and “itches like crazy” unless she sticks to drinking bottled water.
The explanation, it transpires, interestingly enough, is that she has become sensitive to the minuscule amounts of chlorine added to the water supply to kill off bacteria and protozoa that may be lurking in storage tanks or elsewhere. The remedy, gratefully, could not be simpler. Cold reduces the concentration of chlorine, and she has had no further problems since being advised to keep a jug of tap water in the fridge.