Medical brain notes 45

  Tetrodotoxic Poisoning Source ·              Puffer fish: globe fish, balloon fish, blowfish, toad fish. In Japan, a variety of puffer fish called “fugu” ( Fig 33.16 ) is considered a delicacy, but special licensing is required to prepare this extremely toxic fish. ·              Newts: taricha, notophthalmus, triturus, cynops. Salamanders. ·              Blue-ringed octopus ( Hapalochlaena maculosa ) ( Fig 33.17 ): of Australia and Japan is the only known species in which tetrodotoxin has been found in extracts of venom glands, in contrast to being found in the skin, muscle, liver, ovaries, and eggs of other species. ·              Snails: In a study of several outbreaks of tetrodotoxin- associated snail poisoning in Zhoushan city, China, the following snail species were identified as culprits:  Zeuxis samiplicutus, Zeuxis siguinjorensis, Zeuxis variciterus,  and  Z. succinctus . In all the cases, the snails were steamed, boiled, or fried. The incubation period ranged from 5 minutes

  Shellfish Poisoning Source ■■    Shellfish (especially oysters, clams, mussels, and scallops) contaminated by dinoflagellates. Other sources include univalve mollusks, starfish, limpets, sand crabs, whelks, turban shells, top shells, xanthid crabs and various fish. Types Paralytic Shellfish Poisoning There are actually several paralytic shellfish toxins (PSP toxins). PSP toxins are a group of 21 structurally related neurotoxins, and are among the most common and deadly phycotoxins. The main toxin is saxitoxin which is produced by the following dinoflagellates (unicellular algae): Pyrodinium, Gymnodinium and Alexandrium. Because dinoflagellates can occur in tropical and moderate climate zones, shellfish can accumulate these toxins worldwide. While the primary areas of poisoning have been the east and west coasts of the United States and Canada, the area around Japan, and the area from Southern Norway to Spain, of late, reports of paralytic shellfish poisoning (PSP) have been coming in

  Chemicals Chemical contaminants of food include heavy metals, pesticides, and food additives. The last mentioned will be discussed in this section, while the other two entities are discussed elsewhere. Food additives may be  antioxidants, flavouring agents,colouring agents, sweetening agents, thickening agents,  or  preservatives  ( Table 33.11 ). Monosodium Glutamate (MSG) Synonyms Accent, Ajinomoto, Chinese Seasoning, Glutacyl, Vetsin, Zest. Uses ■■    Flavouring agent in foods, especially Chinese food, sausages, canned soup, etc.* MSG is generally sold as a fine, white crystalline substance, similar in appearance to salt or sugar. It has a sweetish saline taste. ■■  MSG has been used to treat patients with hyperammon-aemia in conditions such as hepatic encephalopathy.   Source ·       Glutamate, a major building block of proteins, is released during breakdown of a protein molecule, and occurs naturally in many foods (meat, milk, mushrooms, cheese, tomatoes, etc.). Monosodium gluta

  Substances of Dependence and Abuse Use of psychoactive substances to experience pleasurable effects is not a recent phenomenon, but has been indulged in by human kind for hundreds, even thousands of years. Terminology in the field of substance abuse has changed frequently leading to a great deal of confusion. Therefore, it is necessary to begin this section by defining currently used terms, and to clarify the differences between them. The nomenclature and diagnostic schemes mentioned here -in are based on the 4th edition of Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), and the 10th edition of International Classification of Diseases and Related Health Problems (ICD-10).   DEFINITIONS Substance Dependence Substance dependence arises out of a maladaptive pattern of substance use, leading to a cluster of behavioural, cognitive, and physiological phenomena that develop after repeated intake. It includes a strong desire to take the drug, difficulties in control-ling its

  CLASSIFICATION ·                Ethanol ·                Tobacco ·                Tranquillisers and Sedatives Barbiturates, benzodiazepines, chloral hydrate, chlorme-thiazole, ethchlorvynol, glutethimide, hexapropymate, meprobamate, methyprylon, methaqualone, zolpidem, zopiclone ·                Opiates and Opioids ·                Cocaine ·                Cannabis ·                Amphetamines and “Designer Drugs” ·                Hallucinogens Lysergic acid diethylamide (LSD), phencyclidine, psilo-cybine, bufotenine, mescaline, ketamine, diethyltrypt-amine (DMT) ·                Inhalants Fluorinated hydrocarbons (freons), ethers, ketones, aromatic and aliphatic hydrocarbons ·                Miscellaneous Substances  Caffeine, datura seeds, analgesics, anabolic steroids, cough syrups, laxatives Several of these compounds have been discussed in detail elsewhere, and the reader is advised to consult the  Index  for locating them. The remaining will be discussed inthis section. Globa