mindmap root((TOXI)) toxin A substance produced by a living organism （such as bacteria） that is highly poisonous to other organisms.
🌱Humans eat rhubarb stems without ill effects, while cattle may die from eating the leaves, which seem to contain two different toxins. 🌳Long before chemists started creating poisons from scratch, humans were employing natural toxins for killing weeds and insects. For centuries South American tribes have used the toxin curare, extracted from a native vine, to tip their arrows. The garden flower called wolfsbane or monkshood is the source of aconite, an extremely potent toxin. The common flower known as jimsonweed contains the deadly poison scopolamine. And the castor-oil plant yields the almost unbelievably poisonous toxin called ricin. Today we hear health advisers of all kinds talk about ridding the body of toxins; but they're usually pretty vague about which ones they mean, and most of these "toxins" wouldn't be called that by biologists. toxicity The state of being poisonous; the degree to which something is poisonous.
🌱Though they had tested the drug on animals, they suspected the only way to measure its toxicity for humans was by studying accidental human exposures. 🌳Toxicity is often a relative thing; in the words of a famous old saying, "The dose makes the poison." Thus, it's possible to die from drinking too much water, and lives have been saved by tiny doses of arsenic. Even though botulinum toxin is the most toxic substance known, it's the basic ingredient in Botox, which is injected into the face to get rid of wrinkles. With some poisons, mere skin contact can be lethal; others are lethal when breathed into the lungs in microscopic amounts. To determine if a chemical will be officially called a poison, researchers often use the "LD50" test: If 50 milligrams of the substance for every kilogram of an animal's body weight results in the death of 50% of test animals, the chemical is a poison. But there are problems with such tests, and toxicity remains a very individual concept. toxicology A science that deals with poisons and their effect.
🌱At medical school he had specialized in toxicology, hoping eventually to find work in a crime laboratory. 🌳Even though most of us are aware of toxicology primarily from crime shows on TV, toxicologists actually do most of their work in other fields. Many are employed by drug companies, others by chemical companies. Many work for the government, making sure the public is being kept safe from environmental poisons in the water, soil, and air, as well as unhealthy substances in our food and drugs. These issues often have to do with quantity; questions about how much of some substance should be considered dangerous, whether in the air or in a soft drink, may be left to toxicologists. But occasionally a toxicology task may be more exciting: for instance, discovering that what looked like an ordinary heart attack was actually brought on by a hypodermic injection of a paralyzing muscle relaxant. neurotoxin A poisonous protein that acts on the nervous system.
🌱From her blurred vision, slurred speech, and muscle weakness, doctors realized she had encountered a neurotoxin, and they suspected botulism. 🌳The nervous system is almost all-powerful in the body: all five senses depend on it, as do breathing, digestion, and the heart. So it's an obvious target for poisons, and neurotoxins have developed as weapons in many animals, including snakes, bees, and spiders. Some wasps use a neurotoxin to paralyze their prey so that it can be stored alive to be eaten later. Snake venom is often neurotoxic （as in cobras and coral snakes, for example）, though it may instead be hemotoxic （as in rattlesnakes and coppermouths）, operating on the circulatory system. Artificial neurotoxins, called nerve agents, have been developed by scientists as means of chemical warfare; luckily, few have ever been used.