In toxicology, the median lethal dose, LD50 (abbreviation for "lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a toxin, radiation, or pathogen. The value of LD50 for a substance is the dose required to kill half the members of a tested population after a specified test duration. LD50 figures are frequently used as a general indicator of a substance's acute toxicity. A lower LD50 is indicative of increased toxicity.
Strychnine is a highly toxic, colorless, bitter, crystalline alkaloid used as a pesticide, particularly for killing small vertebrates such as birds and rodents. Strychnine, when inhaled, swallowed, or absorbed through the eyes or mouth, causes poisoning which results in muscular convulsions and eventually death through asphyxia. While it is no longer used medicinally, it was used historically in small doses to strengthen muscle contractions, such as a heart and bowel stimulant and performance-enhancing drug. The most common source is from the seeds of the Strychnos nux-vomica tree.
Ibotenic acid or (S)-2-amino-2-(3-hydroxyisoxazol-5-yl)acetic acid, also referred to as ibotenate, is a chemical compound and psychoactive drug which occurs naturally in Amanita muscaria and related species of mushrooms typically found in the temperate and boreal regions of the northern hemisphere. It is a prodrug of muscimol, broken down by the liver to that much stabler compound. It is a conformationally-restricted analogue of the neurotransmitter glutamate, and due to its structural similarity to this neurotransmitter, acts as a non-selective glutamate receptor agonist. Because of this, ibotenic acid can be a powerful neurotoxin in high doses, and is employed as a "brain-lesioning agent" through cranial injections in scientific research. The neurotoxic effects appear to be dose-related and risks are unclear through consumption of ibotenic-acid containing fungi, although thought to be negligible in small doses.
Rodenticides are chemicals made and sold for the purpose of killing rodents. While commonly referred to as "rat poison", rodenticides are also used to kill mice, squirrels, woodchucks, chipmunks, porcupines, nutria, beavers, and voles. Despite the crucial roles that rodents play in nature, there are times when they need to be controlled.
In excitotoxicity, nerve cells suffer damage or death when the levels of otherwise necessary and safe neurotransmitters such as glutamate become pathologically high, resulting in excessive stimulation of receptors. For example, when glutamate receptors such as the NMDA receptor or AMPA receptor encounter excessive levels of the excitatory neurotransmitter, glutamate, significant neuronal damage might ensue. Excess glutamate allows high levels of calcium ions (Ca2+) to enter the cell. Ca2+ influx into cells activates a number of enzymes, including phospholipases, endonucleases, and proteases such as calpain. These enzymes go on to damage cell structures such as components of the cytoskeleton, membrane, and DNA. In evolved, complex adaptive systems such as biological life it must be understood that mechanisms are rarely, if ever, simplistically direct. For example, NMDA in subtoxic amounts induces neuronal survival of otherwise toxic levels of glutamate.
Aldrin is an organochlorine insecticide that was widely used until the 1990s, when it was banned in most countries. Aldrin is a member of the so-called "classic organochlorines" (COC) group of pesticides. COCs enjoyed a very sharp rise in popularity during and after The Second World War. Other noteworthy examples of COCs include DDT. After research showed that organochlorines can be highly toxic to the ecosystem through bioaccumulation, most were banned from use. It is a colourless solid. Before the ban, it was heavily used as a pesticide to treat seed and soil. Aldrin and related "cyclodiene" pesticides became notorious as persistent organic pollutants.
Tetramethylenedisulfotetramine (TETS) is an organic compound used as a rodenticide. It is an odorless, tasteless white powder that is slightly soluble in water, DMSO and acetone, and insoluble in methanol and ethanol. It is a sulfamide derivative. It can be synthesized by reacting sulfamide with formaldehyde under acidic condition. When crystallized from acetone, it forms cubic crystals with a melting point of 255–260 °C.
Azinphos-methyl (Guthion) is a broad spectrum organophosphate insecticide manufactured by Bayer CropScience, Gowan Co., and Makhteshim Agan. Like other pesticides in this class, it owes its insecticidal properties to the fact that it is an acetylcholinesterase inhibitor. It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act, and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.
Methiocarb is a carbamate pesticide which is used as an insecticide, bird repellent, acaricide and molluscicide since the 1960s. Methiocarb has contact and stomach action on mites and neurotoxic effects on molluscs. Seeds treated with methiocarb also affect birds. Other names for methiocarb are mesurol and mercaptodimethur.
Tutin is a poisonous plant derivative found in New Zealand tutu plants. It acts as a potent antagonist of the glycine receptor, and has powerful convulsant effects. It is used in scientific research into the glycine receptor. It is sometimes associated with outbreaks of toxic honey poisoning when bees feed on honeydew exudate from the sap-sucking passion vine hopper insect, when the vine hoppers have been feeding on the sap of tutu bushes. Toxic honey is a rare event and is more likely to occur when comb honey is eaten directly from a hive that has been harvesting honeydew from passionvine hoppers feeding on tutu plants.
Phenylsilatrane is a convulsant chemical which has been used as a rodenticide. Phenylsilatrane and some of its analogs with 4-substituents of H, CH3, Cl, Br, and CSi(CH3)3 are highly toxic to mice. They have been observed in the laboratory to inhibit the 35S-tert-butylbicyclophosphorothionate (TBPS) binding site (GABA-gated chloride channel) of mouse brain membranes.
Acetamiprid is an organic compound with the chemical formula C10H11ClN4. It is an odorless neonicotinoid insecticide produced under the trade names Assail, and Chipco by Aventis CropSciences. It is systemic and intended to control sucking insects (Thysanoptera, Hemiptera, mainly aphids) on crops such as leafy vegetables, citrus fruits, pome fruits, grapes, cotton, cole crops, and ornamental plants. It is also a key pesticide in commercial cherry farming due to its effectiveness against the larvae of the cherry fruit fly.
Leptophos (O-(4-bromo-2,5-dichlorophenyl) O-methyl phenylphosphonothioate) belongs to the organophosphates and at room temperature it is a stable white solid. It is also known as Phosvel, Abar and Vcs 506. Leptophos was primarily used as a pesticide and fungicide. for rice, cotton, fruit and vegetables until its use was discontinued in 1975 in USA, but still sold in South-Eastern Asia in 1981.
Tetramethylammonium (TMA) is the simplest quaternary ammonium cation. It has the chemical formula [Me4N]+ and consists of four methyl groups attached to a central nitrogen atom. The cation is isoelectronic with neopentane. It is positively-charged and can only be isolated in association with a counter-ion. Common salts include tetramethylammonium chloride and tetramethylammonium hydroxide. Tetramethylammonium salts are used in chemical synthesis and in pharmacological research. It confers no color to its salts.
TBPS (tert-butylbicyclophosphorothionate) is a bicyclic phosphate convulsant. It is an extremely potent GABA receptor antagonist.
IPTBO is a bicyclic phosphate convulsant. It is an extremely potent GABA receptor antagonist that can cause violent convulsions in mice.
Methyl fluoroacetate (MFA) is an extremely toxic methyl ester of fluoroacetic acid. It is a colorless, odorless liquid at room temperature. It is used as a laboratory chemical and as a rodenticide. Because of its extreme toxicity, MFA was studied for potential use as a chemical weapon. The general population is not likely to be exposed to methyl fluoroacetate. People who use MFA for work, however, can breathe in or have direct skin contact with the substance.
TBPO is an extremely toxic bicyclic phosphate convulsant and GABA receptor antagonist. It is the most toxic bicyclic phosphate known, with an LD50 of 36 μg/kg in mice.
Guanitoxin (GNT), formerly known as anatoxin-a(S) "Salivary", is a naturally occurring cyanotoxin commonly isolated from cyanobacteria and causes excess salivation in mammals via inhibition of acetylcholinesterase. Guanitoxin was first structurally characterized in 1989, and consists of a cyclic N-hydroxyguanine organophosphate with a phosphate ester moiety.
Monocrotaline (MCT) is a pyrrolizidine alkaloid that is present in plants of the Crotalaria genus. These species can synthesise MCT out of amino acids and can cause liver, lung and kidney damage in various organisms. Initial stress factors are released intracellular upon binding of MCT to BMPR2 receptors and elevated MAPK phosphorylation levels are induced, which can cause cancer in Homo sapiens. MCT can be detoxified in rats via oxidation, followed by glutathione-conjugation and hydrolysis.
