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Bee sting has a great educational value.
Today, when we think about the toxic substances that first come to mind are synthetic compounds. But to get to know the toxins created a man first, you should consider natural poisons. These substances are divided into two main groups: first enter the body by contact between host and victim (most poisons of vegetable origin), and the second entered through stings or teeth of animals.
On Earth there are over 400 000 species of plants, containing a tremendous variety of organic substances. It is not surprising that some plants contain substances toxic to animals or humans who want to eat them. Indeed, even those plants that we think are harmless, can contain toxins: they can be found either in the parts of plants we don't eat or incorrectly cooked dishes from them. For example, in Apple seeds, peach and cherry seeds contain cyanoglucoside, of which in the interaction with the enzyme b-glycosidase is formed extremely poisonous hydrocyanic acid. Cyanoglucoside can be found also in the leaves and seeds of many other fruit crops, but the edible pulp contains only trace amounts of these potentially dangerous compounds. However, cassava roots, culture, which constitutes an important source of carbohydrates for more than 500 million people, contains a sufficiently large number of cyanoglucosides. Not to get cyanide poisoning, it is necessary to use the right way to handle the roots.
the Eating of poisonous plants may cause a variety of toxic reactions, which, of course, depends on the specific chemical nature of the toxin. These reactions can be relatively mild and limited to, for example, intestinal disorder, and can present a real danger to the life, as in the case of cassava's something that. The effect can be almost instantaneous or accumulated over time. For example, vegetables from the cruciferous, or cabbage (broccoli, Brussels sprouts, cabbage, cauliflower and other), contain quite a lot of thio– and isocyanate substances that prevent iodine in the thyroid gland, and long-term lack of iodine can lead to development of goiter.
the Plants in the course of evolution has got toxins for various reasons, including to counter pathogenic organisms, such as fungi, to prevent eating of herbivorous animals, including man. Since grazing animals often eat the leaves or stems, not the whole plant, unpleasant dining experience quite able to get them to switch their attention to some other plant foods.
unlike herbivores that eat usually only a small part of plants, many carnivorous animals eat their prey whole; therefore, the poisons of their employees the potential victims to protect, often lead to much more serious consequences than a simple intestinal upset. To predators was discourage, animal poisons should have a really powerful impact. For example, the poison contained in the mucus on the skin of frogs-the poison dart frog, or the meat of the puffer fish, it is able to not just convince the predator to choose another source of food, but to kill him.
the nature of the chemical arms race reached its climax in the invention of poisonous animals that don't just contain toxins in its tissues and has got the special anatomical adaptations in order to inject these toxins directly into the body of other animals. Such poisons are divided into four types: cytotoxins that destroy cells; proteolytic that destroys tissue around the bite at the molecular level; hemotoxin harmful to the cardiovascular system; and neurotoxins, affecting the nervous system and the brain.
Some insects (wasps, ants, bees) and fish (lionfish) use poisons introduced into the body of the enemy, for protection, but other animals, such as fish-eating shellfish-cones, spiders and snakes, apply them to immobilize the prey. These poisons are usually a complex mixture of substances that is able to provide a victim impact versatile. A classic example of an animal venom is snake venom, which we'll talk about it now.
Snake – legless and relatively slow moving animal, so hunting for hyperactive rodents (rats or mice) she needs some special tools. Non-venomous snakes are caught fast and sometimes dangerous (mice and rats can bite!) prey through ambush tactics and large force. Boas don't use venom, and bites the prey, instantly wrapped her rings and squeeze, preventing breathing and circulation. Poisonous snakes don't behave that way: quickly typing in the victim of poison, they should just wait until she dies or lose the ability to move.
snake venom is a modified saliva that accumulates in a particular organ and reinforced near toxic proteins. These proteins are quite diverse (at least 25), but the effect of all snake venoms can be divided into two main categories: disturbance of blood circulation and violation of the electrical connections between the nervous system and muscles. So, poison alkoholowych American snakes (e.g. pit vipers) usually affects the circulation, and poison the Asian kraits and African Mambo neurotoxic.
the point of view of toxicology, the bite of a rattlesnake if she decides to enter in a victim their entire supply of venom is an extremely unpleasant thing. In most cases it leads to loss of blood due to the rupture of red blood cells and secondary bleeding. Because of this, also comes the low blood pressure and shock. Proteins snake venom destroys not only the erythrocytes, but other tissue. Around the site of the bite there is bruising and blackening, the swelling, the tissue can be permanently deformed, moreover, the bite is accompanied by very strong pain.
the Bite of this Viper venom which contains a neurotoxin, it doesn't look so bad – but in many cases it is lethal. Neurotoxins raise the bar chemical warfare in the animal body to a completely different level. To fully understand how this happens, you need to remember how the muscles and nerves conduct electrical signals.
the Electrical signals and their distribution: the Achilles heel of the
the Electrical signals arise in the brain and down the spinal. From there they are transmitted to muscles through the processes of nerve cells – the axons. Axon – a kind of living wire that transmits electrical impulses from the spinal cord to the muscles, which may be at a considerable distance from him.
the electric signal from the motor neurons (nerve cells that send signals to the muscles) is as simple as Morse code. But instead of dots and dashes it is, in fact, some point. It might be better to compare it with the binary computer code, where the signal can only be "1" or "0". Nerve signal is a result of the flow of ions, and it is the same in almost all animals. The "point" of the electrical signal creates a power surge followed by a return to the original state. In conductive fabric signal is the change in the polarity or charge of the cell membrane. At rest on the membrane of the axon a small negative charge; when a signal (action potential) across a membrane is positively charged.
the ion Fluxes change with the appearance of the action potential is the result of opening and closing of ion channels. At rest, the concentration of positively charged sodium ions outside the axon is approximately 12 times higher than inside and the concentration of positively charged potassium ions is about 40 times higher inside than outside. Therefore, in the event of the action potential ion-specific channels open in the axon enters the sodium. When the action potential ends of the open channels along which the axon leaves the potassium. Changes in the content of ions inside and outside of the axon during a single action potential is actually a small, but fast movements (e.g. during a marathon) the number of individual capacities, sent by the motor neurons to the muscles of the legs, so huge that the total inflow of sodium and outflow of potassium may begin to reduce the concentration gradient. A constant difference of concentration of ions inside and outside cells is maintained through the work of the sodium-potassium ATP pump that pumps out sodium from the cell and pumps in cell potassium with energy.
In the nerve ending, where the thickened end of the axon is intertwined with the muscle fibre, there are several proteins involved in intercellular interactions required for coordinated movement.
Electrical signal – the action potential, which overcame all the way from the body of the neuron located in the spinal cord, to the end of the axon, slightly changed, so instead of the influx into the cell sodium is the influx of calcium. These ions, in turn, promote release of bubbles (vesicles) from the Golgi apparatus, located in the tip of the axon. Vesicles represent a sphere surrounded by a double lipid membrane containing protein "broth".
having released from the Golgi apparatus, the vesicles migrate to the membrane of the nerve endings and throw its contents in the fluid-filled gap between the membrane of the neuron and membrane of muscle fibers. Almost all animals these vesicles filled with acetylcholine, which then, overcoming the gap between the nerve ending and the muscle fiber, binds to receptor on the membrane of the latter. When stimulated with acetylcholine the receptor opens the channel which through the membrane of the muscle fiber can be sodium, so that an electric "point", transmitted by the neuron, begins the second part of his journey already on the fiber, which ultimately causes it to decline.
the Last in this chain of events – the shutdown of an electrical signal. Acetylcholine reversible joins cholinesterase receptor after its activation may be released again. However, if the molecule acetylcholine remains in the synapse (space between the membranes of the neuron and muscle fiber) is unused, it can reactivate the receptor. To permanently disable this signal substance, it requires another protein enzyme acetylcholinesterase. It is located in the membrane of the muscle fiber. Acetylcholinesterase breaks down the acetylcholine molecule into acetate and choline and, thus, the receptor can no longer activate.
If we consider the whole system, for the origination and conduction of the action potential, stimulating a coordinated movement of muscles, requires neither more nor less than six proteins. In order to place the movement need to work together sodium, potassium and calcium channels, the sodium-potassium pump, the acetylcholine receptor and acetylcholinesterase. Although this system is perfectly configured and is universal for all animals, she still represents the "Achilles ' heel" of the process movement. Substances that can disrupt the function of any of these proteins, can cause uncoordinated spasms and tremor, but a quick death when exposed to the muscles involved in breathing and circulation (heart). So the more elegant the system, the easier it is to arrange in her "plug".
the Clog in the pipes
As we have said, snakes are slow-moving ambush predators, hunting fast and dangerous prey. To equalize the chances of a snake with neurotoxic venom is injected the victim with substances that prevent communication between the nervous and muscular systems. Bitten by a rat or a mouse loses control of their movements, so the snake becomes easy to grab and swallow it. Interestingly, different snake neurotoxins affect different proteins and processes neuromuscular junctions. For example, one of the toxins krait (a-bungarotoxin) irrevocably releases the acetylcholine receptors, while the other (b-bungarotoxin) blocks the release of acetylcholine from vesicles from the Golgi apparatus. The black Mamba venom contains a neurotoxin that, on the contrary, attaches itself to the acetylcholine receptors, not allowing acetylcholine to contact them.
the Chemical arms race – the prerogative of not only snakes. For example, snail-cones from an ambush attack on the fish, pierce it with his retractable trunk and enter conotoxin blocking the inflow of calcium to the nerve endings. But the poison is not only predators. Frogs-the poison dart frog from the tropics of South America secrete epibatidine the surface of the skin. This toxin blocks the acetylcholine receptors of the predator who dared attack the frog, interlocking connections between neurons and muscles. In plant genus of stroobants contains ouabain, is able to inactivate the sodium-potassium pump. Fungi of the genus Anabella produce curare, a toxin that blocks the acetylcholine receptors. Toxins can be found even in bacteria: botulinum toxin A, produced by bacteria Clostridium botulinum, is considered one of the strongest known poisons. Any influence of this substance, even in concentrations as low as nanograms per liter, is deadly because it inhibits the release of acetylcholine from neurons.
the First poisons, I met people, was natural. Some of them have rough action, just destroying cells and tissues, but others are more clever and accurate. Poisons affecting the finely organized nervous system of animals, disrupting one or more of simple proteins cause dramatic consequences.
the Excerpt from the book Alan Coloca "Modern poisons: Dose, action, consequences"
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