Antagonism

ANTAGONISM (from Greek anti- against and agon- struggle), a term used to define the negative interaction or opposition of two phenomena or organisms; it is expressed either directly in their mutual destruction or weakening, or indirectly in the opposite reaction of some biological object to each of these forces. An example of direct antagonism can be the opposition of two microbes when they grow simultaneously on a nutrient medium, when one suppresses the development of the other. Such antagonism is observed, for example, between the anthrax bacillus and the colon bacillus, between phenol-producing microbes and other microbes that do not produce phenol. Examples of indirect antagonism are: 1. Antagonism of microbes in the host organism, e.g., the weakening effect of the blue pus bacillus on the diphtheria bacillus, the frequent suppression of Plasmodium vivax by Plasmodium falciparum. In these cases, the phenomena of antagonism are complicated by the participation of the immune reaction from the host. 2. Muscular antagonism, observed when flexors or extensors act on the same limb. 3. Nervous antagonism, manifested in the action on the same organ of two opposite nervous influences, e.g., vasodilators and vasoconstrictors, the oculomotor nerve that constricts the pupil, and the cervical sympathetic ganglion that dilates the pupils. 4. Poison antagonism, for example, of pilocarpine, which constricts the pupil, and atropine, which dilates it. 5. Ion antagonism - in their action on protoplasm; ions that lower surface tension counteract ions that raise it, and in connection with this stand, for example, the phenomena of contraction of protoplasmic structures. 6. Antagonism of different groups of different organisms that make up animal or plant biocenoses; an example of such antagonism is the displacement of the black rat by the gray rat, etc. G. Epstein. Ion antagonism - the ability of ions present simultaneously in a solution to mutually suppress their characteristic action. In the mineral composition of blood plasma, the main component is sodium chloride (table salt). A solution of this salt was long considered 'physiological' and was used for blood replacement. However, experiments by Ringer long ago showed that a pure solution of sodium chloride at the same concentration as this salt is found in blood is very poisonous for isolated organs (e.g., the heart) of vertebrate animals. Only the addition of small amounts of potassium and calcium chlorides leads to the formation of a physiological solution suitable for preserving organs. Loeb established that NaCl - the main component of sea water - is no less poisonous for marine animals. Particularly important for the doctrine of ion antagonism are Loeb's experiments on the embryo of the marine fish Fundulus. It dies in NaCl solutions just as it does in pure solutions of KCl, CaCl₂ or MgCl₂. In a mixture of these salts (or at least two of them, e.g., NaCl+CaCl₂), as well as in their complete absence (in distilled water), it survives excellently. The latter observation shows that to a certain extent salts are not directly required for the life of the embryo, but play, mainly, a protective role, mutually eliminating the toxicity inherent in each of them. Thus, salts (even seemingly harmless ones like NaCl) are poisonous in pure solutions, but in mixtures, at certain quantitative ratios, they can neutralize each other. Instead of summation (synergism), which is mostly observed in the joint action of several poisonous agents, here there is an antagonistic action of one salt on another. Such neutralizing, antagonistic action is often possessed not only by the normal components of the external aqueous environment, but even by completely unusual for the organism, foreign to it salts, with specific poisonous action, which they manifest at higher concentrations. A solution in which the poisonous action of each salt is completely eliminated by the action of its antagonist is called balanced, or equilibrated (Loeb).-In aqueous solution, salts break down into their constituent parts - electrically charged ions: positively charged cations and negatively charged anions. Antagonistic action must therefore be attributed not to salts as such, but to the ions into which they decompose, in particular to metal cations (usually Na, K, Ca, Mg); it is most manifested between ions of different valence. The phenomena of ion antagonism are very widespread and are observed when salt solutions act on any living tissue. First noticed by Ringer in higher terrestrial animals and carefully studied by Loeb on marine organisms, they have also been found in freshwater animals as well as in plants. The mechanism and nature of ion antagonism are still little clarified. In recent years, similar antagonistic dependencies have been found to occur in the precipitation of colloidal solutions by salt mixtures. Obviously, in the organism, the combination of antagonist salts serves to maintain a certain state of dissolution or swelling of cellular colloids. A distinction should be made between 2 types of ion antagonism. In some cases, each of the two salts separately acts in opposite directions; in the mixture, the opposite effects are balanced. In other cases, representing the most characteristic phenomena of antagonism, each salt separately has the same action, which disappears (or weakens) in the mixture. Lit.: Rubinstein D., Introduction to physicochemical biology, GIZ, M., 1925.

D. Rubinstein. Microbial antagonism, in contrast to microbial symbiosis (see),-a phenomenon consisting in that their joint life proves impossible and one species of microbe displaces another, as a result of which there may occur a complete death of some while others, called antagonists, flourish luxuriantly. Microbial antagonism can be detected by various methods. If two different species of microbes are introduced into a liquid nutrient medium, one of which is an antagonist, for example, the plague bacillus and the blue pus bacillus (the latter will be the antagonist), then after several days the plague bacillus can no longer be detected, which dies, displaced by the blue pus bacillus. Such microbial antagonism can also be detected when various microbes are sown on agar poured onto the surface of a Petri dish, if the sowing is done with crossing streaks; at the crossing point, growth of the antagonist is observed in the absence of growth of the other microbe. Among microbes there are 'specialists'-antagonists. These include cultures of the blue pus bacillus (B. pyocyaneus), cultures of lactic acid bacteria and putrefactive microbes. The mechanism of action of antagonists is different: sometimes they have more rapid reproduction and, being less demanding, outgrow the companion and thus suppress it; sometimes the antagonist produces acid, and thus the reaction of the medium becomes unfavorable for the companion microbe, if the latter poorly tolerates an acidic reaction. This is, for example, the antagonistic action of lactic acid microbes on the intestinal flora, which served as the basis for the intestinal lactobacillus therapy proposed by Metchnikoff. An antagonist can change the medium in the direction of excessive alkalinity, as does, for example, B. pyocyaneus, which also leads to the death of the companions. Or, finally, the antagonist, by producing various enzymes and metabolic products, with the help of the latter, delays the growth of the companion or even kills it. Particularly destructive are the bacteriolytic and peptolytic enzymes produced by microbes; the aforementioned B. pyocyaneus just produces such enzymes, which explains (in addition to changing the reaction of the medium) the exceptional antagonistic action of the culture of this microbe. Schiller also distinguishes the phenomena of 'forcible' microbial antagonism, when bacteria, not manifesting their antagonistic properties under normal conditions, reveal them only artificially.

S. Zlatogorov. Antagonism of poisons means the destruction or weakening of the effect of one poison by another. A distinction is made between chemical-physical A., otherwise antidotism, and physiological. In antidotism, the weakening of the effect is explained by the chemical or physical interaction of substances, in which compounds are obtained that are insoluble or less toxic than those from which they were formed. The antidote to a poison can also be a physiologically indifferent substance. Examples of antidotism can serve acids and neutralizing alkalis, alkaloids and tannic acids that precipitate them, alkaloids and charcoal that adsorbs them, and various physiologically weakly active colloidal substances. Chemical-physical A. can manifest itself both before the absorption of the substance and its penetration into the blood and tissues, and after that; in poisoning with phenol, for example, sodium sulfate is prescribed with the expectation of forming the relatively less toxic salt of phenyl-sulfuric acid. Physiological A., or A. in the narrow sense of the word, manifests itself through the action of both poisons on the cells of the body. This A. can be direct, or true, when both poisons act in opposite directions on the same elements (e.g., excitation by caffeine of many parts of the central nervous system, depressed by alcohol), and indirect, or false, when the decrease in effect occurs when the poisons act on different elements (e.g., curare, by paralyzing the endings of motor nerves, eliminates strychnine convulsions, which depend on the excitation of the central nervous system). A. can be bilateral, when a paralyzing poison weakens the effect of an exciting one, and conversely, itself in its action can be weakened by an exciting one, and unilateral, when only the first phenomenon is observed. An example of bilateral A. is the alcohol and caffeine mentioned above, and of unilateral-pilocarpine and atropine in their application in medium doses to the pupil, when the constriction of the latter, caused by pilocarpine, is eliminated by atropine, while the dilation from atropine is not susceptible to the action of pilocarpine. As a general rule, it can be established that when antagonists are used in small doses, bilateral A. is observed, and in large doses-unilateral A., with the paralyzing POISON prevailing. A. Likhachev.