MICROELEMENTS

From Big Medical Encyclopedia

MICROELEMENTS — the chemical elements which are in fabrics of animal and vegetable organisms in concentration 1: 100 000 and below; carry also chemical elements which in low concentrations are contained in waters, soils and rocks to microelements. Nek-rye M. are absolutely necessary for the most important processes of life activity of the person, and also for normal course of many metabolic reactions and fiziol, functions. The maintenance of a row M. in fabrics and biol, liquids of the person serves as valuable diagnostic test at many diseases. In the medical purposes iodination of sodium chloride for prevention of a local craw and fluoration of drinking water for prevention of caries of teeth was widely adopted. In addition to mass (covering tens of millions of people in the USSR) preventive use of these M., nek-ry M. are used in medical practice as pharmaceuticals (drugs of cobalt and iron — at nek-ry forms of anemias, drugs of iodine — at atherosclerosis, diseases of a thyroid gland etc.). In agriculture the important role of M. in biol, processes is considered during the planning of actions for the purpose of increase in productivity of livestock production and crop production.

In a live organism those M. preferential collect, to-rye are in the environment in the form of the mobile, easily acquired (water-soluble) connections. The Nek-ry chemical elements which are present at soils and rocks in large numbers (Si, Al, Fe, etc.), are M. for plants, animals and the person. M.'s most — metals (Fe, Cu, Co, Zn, Mn, Mo, etc.), nek-ry M. — nonmetals (I, F, Br, Se). In an organism of animals and the person it is revealed the St. 70 chemical elements which are contained in it in macro - and microconcentration. Assume that improvement of analytical methods will allow to find all known chemical elements in vegetable and animal fabrics. However only part M. can be carried to biogenic elements, i.e. the chemical elements which are constantly a part of organisms and players defined biol, a role,

carry To biogenic chemical elements oxygen (see), carbon (see), hydrogen (see), nitrogen (see), calcium (see), phosphorus (see), potassium (see), sulfur (see), chlorine (see), sodium (see), magnesium (see), iron (see), zinc (see), copper (see), iodine (see), fluorine (see), manganese (see), molybdenum (see), cobalt (see), vanadium (see) and selenium (see). Oxygen, carbon, hydrogen, nitrogen, calcium and phosphorus make the ground mass of living material. To biogenic M., i.e. subjects M., to-rye consider necessary for life activity, most often carry iron (Fe), copper (Cu), zinc (Zn), iodine (I), manganese (Mn), cobalt (Co), molybdenum (Mo), selenium (Se), chrome (Cr), nickel (Ni), tin (Sn), silicon (Si), fluorine (F) and vanadium (V).

On value for life activity of an organism of M. divide on absolutely necessary (Co, Fe, Cu, Zn, Mn, I, F, Br) and possibly necessary (Al, Sr, Mo, Se, Ni, Si, V); the role of bismuth (Bi), silver (Ag) and other M. which are naturally found in fabrics remains obscure. However forms of contents in an organism aluminum (see), strontium (cm.), cadmium (see), bromine (see), boron (see), caesium (Cs), barium (see), bismuth (see) and some other, found in living material M., and also their role in implementation of various functions of animal and vegetable organisms are studied insufficiently. Approximately only for one third of all M. there are rather convincing proofs that they play a part in processes of life activity of a human body.

M.'s distribution in an organism is caused by their chemical properties and therefore it is very various. Biologically significant M.' most is a part enzymes (see), vitamins (see), hormones (see), respiratory pigments (see). The most important and well studied connections M. in a human body are hemoglobin (see), myoglobin (see), hemocyanin and other respiratory pigments, and also hemosiderin, the transferrin containing Fe; polifenoloksidaza and others oxidases (see), the containing Cu; karboangidraza (see), insulin (see), the containing Zn; cyanocobalamine (see), the containing Co; thyroxine (see), supporting I.

M.'s accumulation in this or that body is considerably connected with fiziol, this M.'s role and specific activity of body (e.g., preferential accumulation of Zn in gonads and its influence on reproductive function). Often M. are a part of highly mineralized tissues of skeleton, joining in crystals of apatite (F, Sr, etc.), and in nek-ry cases influence properties of these fabrics. In other cases of M. influence the bodies and functions which are not connected with the place of their deposition in an organism.

Action of M. which are a part of physiologically active connections is shown by hl. obr, in their influence on a metabolism. It is established that nek-ry M. influence human height, animals (Mn, Zn, I) and plants (Mn, B, Cu); on reproductive function of animals (Mn, Zn) and plants (Mn, Cu, Mo), on processes of tissue respiration (see. biological oxidation ), hemopoiesis (see), intracellular exchange.

There are M. (Mo, In, etc.), ability to-rykh to influence vital processes at animals and plants is authentically established, however their role for life activity of a human body is not found out.

Under natural conditions areas, so-called meet. biogeochemical provinces (see) where owing to the raised or lowered M.'s maintenance in the soil and other objects of the environment mass diseases (endemia) among animals and plants are observed. Of an endemia can strike with Nek-rye both animals, and the person: excess of fluorine in drinking water causes in the person and domestic animals fluorosis (see); a lack of iodine of the soil, vegetation and foodstuff — a local craw (see. Craw local ). It is possible to note that honor in all cases when local incidence among people takes place, it is possible to find adequate symptoms of a disease as well at the animals living in this area - Opposite, in the presence of local diseases among animal people is surprised optional as its diet, as a rule, only to a certain extent consists of products of local production. An exception of this rule can be only nek-ry an endemia of a fluorosis, at to-rykh the person and animals use different water sources with the unequal maintenance of F.

The mechanism of development of local diseases in animals and the person results an is as follows: lack or M.'s surplus of the soil and water in deficit or their surplus in a diet, and from here and in an organism. At the same time there are changes in extent of assimilation of M., in their metabolism — distribution in fabrics and removal from an organism, easing or strengthening of synthesis of biologically active agents, to-ry is accompanied by any M.'s exchange, change of intensity of the exchange processes depending on M., adaptation to deficit or any M.'s surplus or development of the frustration typical for this or that local disease.

For the person only two M. of a natural origin which are the reason of local frustration are known. It is fluorine, excess receipt to-rogo in an organism leads to a fluorosis, and iodine, a shortcoming to-rogo promotes emergence and spread of a local craw. In literature there are separate instructions for a role and other M. in pathology of the person: excess of molybdenum is connected with gout, vanadium — with prevalence of caries, strontium — with Kashin's disease — Beck (see. Kashina — Beck a disease ) etc., however there are no proofs of a role of these M. in development of the listed diseases.

In 60 — the 70th 20 century works on studying of changes of maintenance of M. in bodies and tissues of the person at various diseases were widely carried out, napr, at infectious hepatitis. Establishment of the numerous facts of change of maintenance of M. in blood and other fabrics at this or that form of pathology was result of such works. However these and similar researches did not give and, apparently, cannot furnish the clue to M.'s use in the medical or preventive purposes as change of maintenance of M. in an organism at the majority of the studied diseases is a consequence, but not a cause of illness. Besides concentration of many M. which are not giving in to homeostatic regulation in blood and other fabrics: in a decisive way depends on this M.'s arrival with water and food at present, and for osteotropny and other M. with long biological half-life — and in the past. Other often found mistake at researches M. in an experiment on animals and at interpretation of experimental data is the insufficient accounting of a dose, form of connection, a rhythm and ways of introduction M. Tak, numerous data of experimenters on ability of fluorine to influence function of a thyroid gland, the liver, a nervous system etc. cannot be extended to natural conditions of the increased intake of fluorine with water in the endemic centers of a fluorosis where, despite a set of inspections, it is not possible to note similar deviations. Similar discrepancy of experimental data and results of natural observations is explained by the fact that even minor changes of concentration of fluorine in water considerably change its influence on an organism: at increase in maintenance of F in water to 1,0 — 1,5 mg/l he shows the expressed anti-carious action, at further increase in concentration up to 2,0 — 3,0 mg/l positive anti-carious effect of fluorine stops, undesirable effects in the form of the expressed forms of a fluorosis and secondary increase in prevalence of caries on the basis of the teeth destroyed by a fluorosis begin to appear.

Closely the problem of biogeochemical endemiya and M. is adjoined by a question about so naz, technogenic local provinces, to-rye arise at environmental pollution. The cases of local diseases in Japan and other countries caused by accumulation in the environment of mercury, lead, cadmium, arsenic and other metals are known. Apparently, it is possible to expect further cases of defeat of the person, animals and flora of M., hit to-rykh to the environment is caused by economic activity of the person if vigorous measures for environmental control from anthropogenous pollution are not taken. In nek-ry cases can arise from M.'s influence both a natural, and technogenic origin (the fluorosis known earlier only in areas where water contains a lot of fluorine, is registered nowadays and in areas of pollution of the air basin emissions of aluminum production, products of combustion of nek-ry types of the solid fuel rich with fluorine, etc.).

The main source of arrival of M. in a human body — foodstuff of plant and animal origin. Drinking water covers only 1 — 10% of daily need for such M. as I, the SI, Zn, Mn, Co, Mo, and only for separate M. (F, Sr) can be the main source of their receipt in an organism. Different M.' maintenance in a diet depends on geochemical conditions of the area, in a cut products, and also were received from a set of the foodstuff entering a diet. Inclusion in a diet of various food stuffs, a part from is characteristic of the population of the developed countries to-rykh it is made in other biogeochemical areas in view of what the conditions promoting impact on the person of biogeochemical features of this area are liquidated. The main source of receipt in an organism of cobalt is milk, iodine — milk and vegetables, other major M.' most — bakery products and other products of plant origin.

With age many M.' maintenance (Al, Cl, Pb, F, Sr, Ni) in body tissues increases, and during intensive growth and development of an organism this increase goes rather quickly, and by 15 — 20 years is slowed down or stops. There are data that the maintenance of Co, Cu, Ni in blood and Sr in a skeleton at the age of 50 — 60 years becomes slightly lower, than at the age of 20 — 25 years. The absolute maintenance of M. in bodies and fabrics can significantly fluctuate depending on the residence, constant diets and other reasons determining the level of receipt and this M.'s accumulation and also depending on specific features of an organism. It is established that concentration in blood of nek-ry elements is constantly maintained at rather stable level (From 0,1 — 4 — 8 mkg of %, the SI of 70 — 150 mkg of %, Fe of 80 — 120 mkg of %); other M. (Sr, Pb, F) are not exposed to similar regulation, and their content in blood can fluctuate considerably depending on the level of receipt of an element in an organism. In blood M.'s most is in the state connected with proteins — Cu as a part of kuproproteid and ceruloplasmin, Zn — as a part of coal anhydrase (karboangidraza), Co — as a component of cyanocobalamine and in the form connected with protein, iron — as a part of hemoglobin, in the form of siderophilin. Nek-rye M. in blood in the ionized state, e.g. Li are; apprx. 50% of all Sr and F is included into mineral structures of bones, enamel and dentine.

Functions M in an organism are very responsible and diverse. The Fiziologo-gigiyenichesky characteristic of the major M. is presented in the table where effects of so-called biotic number of M. are given (i.e. the number of M. which are found in the nature); in these limits action of the same element can significantly change. E.g., trace amounts of Mn stimulate a hemopoiesis and an immunoreactivity, big — oppress them.

If M. come to an organism in the quantities exceeding biotic, i.e. physiologically necessary for an organism, they can influence not those systems and functions, on to-rye they influence under natural conditions. Fluorine — one of the microelements which are fullestly studied and widely applied in the preventive purposes is in this respect very indicative.

In an organism interaction is noted also between M. (e.g., With effectively affects a hemopoiesis only in the presence in an organism of enough Fe and Cu; Mn increases assimilation of Cu; Cu on a nek-eye to effects is an antagonist of Mo; F influences metabolism of Sr, etc.). M.'s effect considerably depends also on a way of receipt to an organism (with food, inhaled air, parenterally).

M.'s use in a wedge, medicine has still limited character. The drugs Co, Fe, Cu, Mn are effectively used in fight against nek-ry types of anemias. As pharmaceuticals in clinic use also Br and I. In range of application of M. progress of hygiene is considerable: iodination of salt or bread for prevention of a local craw, fluoration of water (see) for decrease in incidence caries of teeth (see). The fluoration of drinking water which is widely applied in the USSR and many other countries of the world is the most effective method of prevention of caries. In cases when natural waters contain many F, apply the defluorinating installations (see. Defluorination of water ). The problem of determination of optimum levels of receipt of most of M. still waits for the decision. The growing organism especially needs necessary biogenic M. The following factors are most important in this respect: alimentary security of the child and season. Alimentary security of M. is substantially caused by zone biogeochemical features. Season exerts a certain impact on M.'s balance at healthy children. E.g., in spring time the negative balance of iron in connection with insufficient arrival of this M. with food (restriction in a diet of fruit and vegetables), etc. is noted.

M.'s exchange at a fruit and the newborn is closely connected with the state of health and a metabolism of the pregnant woman and the nursing mother. During pregnancy the fruit receives necessary M. through a placenta and deposits them in a liver, a spleen, a bone tissue, marrow etc. In an organism of a fruit about 30% are deposited: arriving with blood of mother of M. Osobenno intensively this deposition goes in recent weeks pregnancies therefore at premature children M.'s stocks are lower, than at full-term. M.'s accumulation in fabrics and bodies of a fruit causes depletion of an organism of mother by the same M. in this connection need full balanced and concerning M. of food of the pregnant woman shall be once again emphasized. Nek-ry M.' maintenance (e.g., gland, copper), in a liver of newborns is 20 times higher, than in a liver of mother.

Various pathology of pregnancy (toxicoses, a Rhesus factor conflict, a perenashivaniye) has an adverse effect on M.'s balance of a fruit. At toxicoses of pregnancy the fruit receives from mother much less blood, than at normally proceeding pregnancy therefore in an organism of a fruit less than A M is deposited. Existence of the pathology which is not connected with pregnancy exerts adverse impact on M.'s exchange at the pregnant woman, in particular on exchange of copper, cobalt and iron that has in turn an adverse effect on fetation.

At embrio-and fetopathies in system mother — a placenta — a fruit M.'s exchange is broken: in blood of women, in a placenta, in the majority of fabrics of a fruit deficit of copper, zinc, cobalt, iron is revealed. At a fruit in the presence of malformations M.'s redistribution is broken: in its fabrics and bodies along with one M.' accumulation (cobalt, iron) there is a deficit of others (copper, zinc). In blood of postmature newborns increase in concentration of copper and manganese in comparison with norm is observed.

In the post-natal period M.'s balance of the child is influenced not only by M.'s stocks in depot, but also M.'s maintenance in breast milk, on a cut alimentary security of M. of mother in turn influences.

Many M.' balance at the newborn is negative since emptying of depot M. happens more intensively, than M.'s arrival to breast milk. The negative balance of most of M. at the newborn is aggravated with artificial feeding, infections, avitaminosis, dispeptic frustration.

M.'s deficit in an organism of mother and a fruit is premises to M.'s use with the medical purpose. Enrichment of diets of pregnant M. (copper, manganese, zinc, cobalt) in biotic doses, i.e. in the doses corresponding fiziol, to requirements of an organism, favorably affects these M.' exchange, leading to normalization of their contents in biol, liquids, and tissues of mother and a fruit.

At the baby M.'s exchange is very intense what the high percent of deduction of M. arriving with food in an organism, dominance of their renal removal over intestinal, and also increase of activity of metallic enzymes testifies to (catalases, karboangidraza, ceruloplasmin).

At children with low body weight at the birth the reduced number of M. in fabrics in comparison with M.'s number at the children who were born with a normal weight comes to light. M.'s exchange at the premature children, twins and children who were born differs from mothers at whom pregnancy was complicated by a nephropathy! special instability. Frequency of negative balance of M. (e.g., copper or iron) at these children is higher, and their concentration in blood and keeping in depot is lower, than at the children who were born from mothers, at to-rykh pregnancy was monocarpic, is not complicated by toxicosis, duration of gestation more than 30 weeks. Preferential intestinal way of allocation of all M. at premature children gives the grounds to assume that it is available for them as disturbance of absorption of M. in went. - kish. a path, and increase in their excretion with bile. Endogenous deficit of a row M. (iron, cobalt, copper, zinc) at premature exerts the oppressing impact on function of marrow and contributes to development in premature children of anemias, frustration of food, rickets etc.

At anemias the change of maintenance of M. (reduction of iron, copper, manganese, nickel, silver, titanium, zinc) or which is response of an organism to the developing pathology, or caused by exhaustion of stocks and the insufficient maintenance of M. in the main depots and insufficient receipt them from the outside is revealed. At children of early age M.'s stocks are exhausted much quicker that is caused by the intensive growth of children, especially if this process is followed by insufficient arrival of M. with food. Endogenous deficit of iron at mother or disturbance of its exchange in her organism are connected usually with hron, inflammatory processes or with disbolism in system mother — a placenta — a fruit that is observed at toxicoses of the second half of pregnancy.

At children of early age with a hypotrophy decrease in content in whole blood of copper and manganese that it is connected as believe, with disturbance of their absorption is revealed.

At rickets M.'s deficit in a diet of the child increases sensitivity of an organism to D - vitamin-nym to drugs owing to what even moderate doses of such drugs can lead to D-vitamin intoxication that needs to be considered. At children about a wedge, a picture of a D-hypervitaminosis in blood find decrease in a copper content, iron, manganese, molybdenum, nickel, cobalt, zinc, manganese in comparison with norm.

At acute went. - kish. diseases the decrease in maintenance of M. in blood (copper, iron, magnesium) depending on age of the child, weight of disease, type of dehydration, type of feeding is observed. Intestinal toxicoses are characterized by the expressed deficit of copper, magnesium, iron in an organism.

M.'s rationing in a diet of children causes certain difficulties because the data on the daily need of a children's organism for separate M. which are available in literature differ in considerable discrepancies. Especially complex challenge is definition of need for M. of children of the first year of life since it is unknown what part M. arrives in the alimentary way and what part the organism scoops from the stocks. Definition of adequacy of a diet of the child to the needs of the growing organism for M. is complicated also by lack of rather exact information on M.'s maintenance in foodstuff of various biogeochemical zones of the country.

As babies of the first half of the year have lives, being on natural feeding, the wedge, signs of insufficiency of M. is not observed, it is possible to assume that breast milk contains enough M. for satisfaction of requirements of the growing organism in this age.

See also Mineral metabolism .

Table. Main fiziologo-hygienic characteristics of the major microelements

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V. A. Knizhnikov; A. A. Muravyev, H. A. Tyurin (ped.).

Яндекс.Метрика