Radiation energy. General information about solar radiant energy and its application. The general biological effect of ultraviolet rays on humans is expressed in three ways:

A significant part of solar radiation reaching the Earth covers the wave range within 0.15 - 4.0 mmk. The amount of solar energy arriving at the Earth's surface at right angles is called the solar constant. It is equal to 1.4·10-3 J (m2/s).

Most of the radiation in the visible region of the spectrum reaches the earth's surface, 30

% - infrared and long-wave ultraviolet. The Earth's surface reaches:

Infrared rays (f - 3·10v11 Hz, - 3·10v12, λ from 710 - 3000 nm) – 45% (IR-

radiation is 50% of the Sun's radiation).

Visible rays (3 10v12 – 7.5 10v 16, λ 400 – 710 nm) – 48%

Ultraviolet rays (7.5 10v 16-10v17, λ 400-10 nm) -7%.

A small portion of solar radiation escapes back into the atmosphere. The amount of reflected radiation depends on the reflectivity (albedo) of the surface. Thus, snow can reflect 80% of solar radiation, so it heats up slowly. A grassy surface reflects 20%, and dark soils only 10 5 of incoming radiation.

Most of the solar energy absorbed by soil and water bodies is spent on water evaporation. When water condenses, heat is released, which warms the atmosphere. Heating of the atmosphere also occurs due to the absorption of 20-25% of solar radiation.

Infrared radiation.

Infrared radiation (IR radiation) is electromagnetic radiation invisible to the human eye. The optical properties of a substance in IR radiation differ significantly from those in the visible spectrum. For example, a layer of water several cm thick is impenetrable to IR radiation with λ >1 μm.

About 20% of the infrared radiation of the solar spectrum is absorbed by dust, carbon dioxide and water vapor in the 10-kilometer layer of the atmosphere adjacent to the Earth's surface. In this case, the absorbed energy is converted into heat.

IR radiation makes up most of the radiation from incandescent lamps (unbearable heat when filming in sound stages) and gas-discharge lamps. IR radiation is emitted by ruby ​​lasers.

The long-wave part of infrared radiation (> 1.4 µm) is retained mainly by the superficial layers of the skin, causing a burning sensation (heat rays). The medium- and short-wave part of IR rays and the red part of optical radiation penetrate to a depth of 3 cm. With large amounts of energy, they can cause overripening. Sunstroke is the result of local overheating of the brain.

Visible radiation is light.

Approximately half of the radiation comes from waves with wavelengths between 0.38 and 0.87 mmk. This is the spectrum visible to the human eye and perceived as light.

One of the visible aspects of the impact of radiant energy is illumination. It is known that light heals the environment (including its bactericidal effect). Half of the sun's total thermal energy is contained in the optical part of the solar radiant energy. Light is necessary for the normal functioning of physiological processes.

Effect on the body:

Stimulates vital activity;

Strengthens metabolism;

Improves overall well-being;

Improves mood;

Increases performance.

Lack of light:

Negative effect on the functions of the nerve analyzer (its fatigue increases):

Increased central nervous system fatigue;

Labor productivity decreases;

Occupational injuries are increasing;

Depressive states develop.

WITH Insufficient awareness is currently associated with a disease that has several names:“autumn-winter depression”, “emotional seasonal illness”, “seasonal affective disorder” (SAD). The lower the natural illumination of the area, the more common this disorder is. According to statistics, 5-10% of people have signs of this symptom complex (75% are women).

Darkness leads to the synthesis of melatonin, which in healthy people regulates the timing of nighttime sleep cycles so that it is healing and promotes long life. However, if melatonin production does not stop in the morning due to the influence of light on the pineal gland, lethargy and depression develop during the day due to inappropriately high daytime levels of this hormone.

Signs of SAD:

Signs of depression;

Difficulty waking up;

Decreased productivity at work;

Reduced social contacts;

Increased need for carbohydrates;

Weight gain.

There may be a decrease in the activity of the immune system, which is manifested by an increase in susceptibility to infectious (viral and bacterial) diseases.

These signs disappear in spring and summer, when the length of daylight increases significantly.

Autumn-winter depression is currently treated with light. Light therapy with an intensity of 10,000 lux in the morning gives a good effect. This is approximately 20 times higher than normal indoor illumination. The choice of duration of therapy is individual for each person. Most often, the procedure lasts 15 minutes. During this time, you can do any activity (read, eat, clean the apartment, etc.). A positive effect is observed within a few days. All symptoms completely stop after a few weeks. Side effects may include headaches.

The effect of treatment is associated with the regulation of the activity of the pineal gland, which modulates the production of melatonin and serotonin. Melatonin is responsible for falling asleep, and serotonin is responsible for waking up.

Also shown:

Psychotherapy;

Antidepressants.

IN At the same time, another type of disturbance of biological rhythms associated with modern lifestyle may currently be observed. Prolonged artificial light leads to a decrease in the inhibitory effect of melatonin on the activity of the gonads. This helps speed up puberty.

Ultraviolet (UV) radiation

Ultraviolet radiation belongs to the short-wave part of the solar spectrum. It borders, on the one hand, with the softest part of ionizing radiation (X-rays), and on the other, with the visible part of the spectrum. Makes up 9% of all energy emitted by the Sun. At the border with the atmosphere, 5% of natural sunlight is absorbed, 1% reaches the Earth's surface.

Ultraviolet radiation from the Sun ionizes the gases in the upper layers of the Earth's atmosphere, which leads to the formation of the ionosphere. Short UV rays are blocked by a layer of ozone at an altitude of about 200 km. Therefore, only rays of 400-290 nm reach the earth's surface. Ozone holes allow the short-wavelength part of the UV spectrum to penetrate.

The intensity of action depends on:

Geographic location (latitude);

Time of day,

Weather conditions.

The biological properties of UV radiation depend on the wavelength. There are 3 ranges of UV radiation:

1. Region A (400-320 nm) - fluorescent, tanning. This is long-wave radiation, which is the dominant part. It is practically not absorbed in the atmosphere, therefore it reaches the Earth's surface. It is also emitted by special lamps used in solariums.

Action:

Causes the glow of some substances (luminophores, some vitamins);

Weak general stimulating effect;

Conversion of tyrosine into melanin (protection of the body from excess UV radiation).

The conversion of tyrosine to melanin occurs in melanocytes. These cells are located in the basal layer of the epidermis. Melanocytes are pigment cells of neuroectodermal origin. They are distributed unevenly throughout the body. For example, in the skin of the forehead there are 3 times more of them than in the upper limbs. Pale people and dark-skinned people contain the same number of pigment cells, but the content of melanin in them is different. Melanocytes contain the enzyme tyrosinase, which is involved in the conversion of tyrosine to melanin.

2. Region B (320 – 280 nm) – mid-wave, tanning UV radiation. A significant part of this range is absorbed by stratospheric ozone.

Action:

Improving physical and mental performance;

Increased nonspecific immunity;

Increasing the body's resistance to the action of infectious, toxic, carcinogenic agents.

Strengthening tissue regeneration;

Increased growth.

This is due to the stimulation of amino acids (tyrosine, tryptophan, phenylalanine, etc.), pririmidine and purine bases (thymine, cytosine, etc.). This leads to the breakdown of protein molecules (photolysis) with the formation of biologically active substances (choline, acetylcholine, histamine, etc.). BAS activate metabolic and trophic processes.

3. Region C (280 – 200 nm) – short-wave, bactericidal radiation. It is actively absorbed by the ozone layer of the atmosphere.

Action:

Vitamin D synthesis;

Bactericidal action.

Other types of UV radiation, as well as visible radiation, have a bactericidal effect, although less pronounced.

N!B! Mid- and short-wave UV rays in large doses can cause changes in nucleic acids and lead to cellular mutations. At the same time, long-wave radiation promotes the restoration of nucleic acids.

4. Region D (315 – 265 nm) is also distinguished, which has a pronounced antirachi-

tic action.

It has been shown that to satisfy the daily requirement for vitamin D, about 60 minimum erythemal doses (MED) are needed on exposed areas of the body (face, neck, arms). To do this, you need to stay in sunlight every day for 15 minutes.

Lack of UV radiation leads to:

Rickets;

Reducing general resistance;

Metabolic disorders (including osteoporosis?).

Excess UV radiation leads to:

Increased need of the body for essential amino acids, vitamins, Ca salts, etc.;

Inactivation of vitamin D (translation of cholecalceferol into indifferent and toxic substances);

The formation of peroxide compounds and epoxy substances, which can cause chromosomal aberrations, mutagenic and carcinogenic effects.

Exacerbation of some chronic diseases (tuberculosis, gastrointestinal tract, rheumatism, glomerulonephritis, etc.);

Development of photophthalmia (photoconjunctivitis and photokeratitis) 2–14 hours after irradiation. The development of photophthalmia can be as a result of the action of: A - direct sunlight, B - scattered and reflected light (snow, sand in the desert), C

– when working with artificial sources;

Dimerization of the protein crystallin (crystallin), which induces the development of cataracts;

There is an increased risk of retinal damage in individuals with a removed lens (even area A).

In persons with fermentopathy to dermatitis;

Development of malignant skin tumors (melanoma, basal cell carcinoma, squamous cell carcinoma),

Immunosuppression (changes in the ratio of lymphocyte subpopulations, a decrease in the number of Langerhans cells in the skin and a decrease in their functional activity) → a decrease in resistance to infectious diseases,

Accelerated skin aging.

Natural protection of the body from ultraviolet radiation:

1. The formation of tanning associated with the appearance of melanin, which:

capable of absorbing photons and thus weakening the effect of radiation;

is a trap for free radicals formed during skin irradiation.

2. Keratization of the upper layer of skin followed by peeling.

3. Formation of the trans-cis form of urocanic (urocaic) acid. This compound is capable of capturing UV radiation quanta. It is excreted in human sweat. In the dark, a reverse reaction occurs with the release of heat.

The criterion for skin sensitivity to UV radiation is the tanning burn threshold. It is characterized by the time of initial exposure to UV radiation (that is, before the formation of pigmentation), after which error-free DNA repair is possible.

IN middle latitudes are distinguished 4 skin types:

5. Particularly sensitive fair skin. It turns red quickly and doesn't tan well. Individuals are distinguished by blue or green eyes, the presence of freckles, and sometimes red hair. Tanning burn threshold – 5-10 minutes.

6. Sensitive skin. People of this type have blue, green or gray eyes, light brown or brown hair. The burn threshold for tanning is 10-20 minutes.

7. Normal skin (20-30 min.). People with gray or light brown eyes, dark brown or brown hair.

8. Insensitive skin(30-45 min.). Individuals with dark eyes, dark skin and dark hair color.

Modification of skin photosensitivity is possible. Substances that increase the skin's sensitivity to light are called photosensitizers.

Photosensitizers: aspirin, brufen, indocid, librium, bactrim, lasix, penicillin, plant furanocoumarins (celery).

Risk groups for developing skin tumors:

light, slightly pigmented skin,

sunburn received before the age of 15 years,

the presence of a large number of birthmarks,

the presence of birthmarks more than 1.5 cm in diameter.

Although ultraviolet irradiation is of primary importance in the development of malignant neoplasms,

skin, a significant risk factor is contact with carcinogenic substances -

mi, such as nickel contained in atmospheric dust and its mobile forms in the soil.

Protection against excessive UV exposure:

1. It is necessary to limit the time spent under intense sunlight, especially in the period of 10.00 - 14.00 hours, the peak for UVR activity. The shorter the shadow, the more destructive the UVR activity.

2. Sunglasses (glass or plastic with UV protection) should be worn.

3. Application of photoprotectors.

4. Application of sunscreens.

5. A diet high in essential amino acids, vitamins, macro- and microelements (primarily nutrients with antioxidant activity).

6. Regular examination by a dermatologist for people at risk of developing skin cancer. Signals for immediate contact with a doctor are the appearance of new

dark spots, loss of clear boundaries, changing pigmentation, itching and bleeding.

It must be remembered that UV radiation is intensely reflected from sand, snow, ice, concrete, which can increase the intensity of UV exposure by 10-50%. It should be remembered that UVR, especially UVA, affects humans even on cloudy days.

Photoprotectors are substances with a protective effect against damaging UV radiation. The protective effect is associated with the absorption or dissipation of photon energy.

Photoprotectors;

Para-aminobenzoic acid and its esters;

Melanin obtained from natural sources (such as mushrooms). Photoprotectors are added to sunscreens and lotions.

Sunscreens.

There are 2 types - with a physical effect and with a chemical effect. The cream should be applied 15-30 minutes before sunbathing, and again every 2 subsequent hours.

Physical sunscreens contain compounds such as titanium dioxide, zinc oxide and talc. Their presence leads to the reflection of UVA and UVB rays.

Sunscreens with a chemical effect include products containing 2-5% benzophenone or its derivatives (oxybenzone, benzophenone-3). These compounds absorb UVR and as a result break into 2 parts, which leads to the absorption of UVR energy. A side effect is the formation of two free radical fragments, which can damage cells.

Sunscreen SPF-15 filters out about 94% of UVR, SPF-30 blocks 97% of UVR, mainly UVB. UVA filtration in chemical sunscreens is low, accounting for 10% of UVB absorption.

Radiation. Radiant energy has a serious effect on microorganisms. Sunlight promotes the vital activity of a group of phototrophic microbes, in which biochemical reactions occur under the influence of solar energy. Most microorganisms are photophobic, that is, afraid of light. Direct sunlight has a detrimental effect on microbes, as evidenced by Buchner's experience. It consists of inoculating a bacterial culture onto an agar plate, placing pieces of dark paper on the bottom of the cup, and shining the cup with direct sunlight for 1-2 hours from the bottom, after which it is incubated. Bacterial growth is observed only in areas corresponding to the pieces of paper. The destructive effect of sunlight is primarily associated with exposure to ultraviolet radiation with a wavelength of 234 - 300 nm, which is absorbed by DNA and causes dimerization of thymine. This action of ultraviolet rays is used to neutralize air in various rooms, hospitals, operating rooms, wards, etc.

Ionizing radiation also has a detrimental effect on microorganisms, but microbes are highly resistant to this factor and are radioresistant (their death occurs when irradiated in doses of 10,000 - 100,000 R). This is associated with the small size of the target due to the low content of nucleic acids in microorganisms. Ionizing radiation is used to sterilize some biologically active substances and food products. The advantage of this method is that during such processing the properties of the processed object do not change.

Drying is one of the factors regulating the content of microorganisms in the external environment. The attitude of microbes to this effect depends largely on the conditions in which it occurs. Under natural conditions, drying has a detrimental effect on vegetative forms of bacteria, but has virtually no effect on spores, which can persist in a dried state for decades. During the drying process, vegetative cells lose free water and denaturation of cytoplasmic proteins occurs. However, many bacteria, especially pathogenic ones, can be well preserved in a dried state, being in pathological material, for example, in sputum, which forms something like a case around the bacterial cells.

When dried from a frozen state in a vacuum, microorganisms retain their viability well, which is associated with the transition to a state of suspended animation. This method of freeze-drying is widely used to preserve museum cultures of microorganisms.

Pressure. Microorganisms are resistant to high atmospheric pressure, due to which they are able to exist and develop at great depths - up to 10,000 m. Microorganisms tolerate high hydrostatic pressure well - up to 5,000 atm.

Ultrasound. When microorganisms are treated with ultrasound, cell death is observed due to their disintegration. It is believed that under the influence of ultrasound, cavitation cavities are formed in the cell, in which high pressure is created, which leads to the destruction of cell structures.

Of the electromagnetic wave energy emitted by the sun, only 1% of ultraviolet rays, 39% of visible light rays and 60% of infrared rays reach the earth's surface. The rest is reflected, scattered, or absorbed by the atmosphere. The voltage of solar radiation depends on the angle of incidence of light and the transparency of the atmosphere, on the time of day and year. When atmospheric air is polluted with dust and smoke, up to 20-40% is retained, and window glass retains up to 90% of the most valuable ultraviolet radiation.

The biological effect of solar radiation on the animal’s body is associated with its qualitative composition at the Earth’s surface. The sun's rays have thermal and chemical effects. Thermal effects come more from infrared rays, and chemical effects come from ultraviolet rays. These rays have different depths of penetration into the skin and tissues of the animal body. Infrared rays penetrate most deeply (up to 2 - 5 cm). They are used in therapy for deep tissue heating or heating of newborns and young animals.

Light rays penetrate several millimeters into the skin, while ultraviolet rays penetrate only tenths of millimeters into the skin.

The effect of sunlight on animals is very important and varied. Its rays cause irritation of the optic nerve, as well as sensitive nerve endings embedded in the skin and mucous membranes. In addition, they stimulate the nervous system and endocrine glands and through them act on the entire body. Under the influence of sunlight in animals, the activity of oxidative enzymes increases, respiration deepens, they absorb more oxygen, and release more carbon dioxide and water vapor. In the peripheral blood the number of red blood cells and hemoglobin increases. The digestion of feed and the deposition of protein, fat and minerals in the tissues are also enhanced.

With a lack of light, the body experiences light starvation, which greatly affects the metabolism. As a result, productivity and resistance to disease are significantly reduced, sluggish wound healing, the appearance of skin diseases, and stunted growth in young animals are noted. In early spring, due to the weakening of the body's defenses caused by a sharp decrease in the intensity of sunlight in the previous winter months, the number of respiratory diseases in animals increases, and the spread of certain infections is observed. Therefore, during the winter months, animals are regularly released for walks in the open air during the sunniest hours of the day. Light starvation is most rarely observed when cattle are kept free-stall and pigs are kept free-range. Light rays also have a significant impact on the reproductive abilities of animals.

However, very strong lighting is not indifferent to animals, so fattened animals are kept in moderately lit and even darkened rooms.

Too bright sunlight has adverse effects on animals not accustomed to it in the form of burns and sometimes sunstroke. To protect animals from sunstroke, shady canopies are installed, the shade of trees is used, and heavy work on horses is abolished during the hottest hours of the day.

Animals, especially birds, are very sensitive to the duration and intensity of the light regime. Therefore, in the practice of industrial poultry farming, the light regime has been clearly developed in accordance with the physiological state of the bird.

The ultraviolet part of the solar spectrum is of great importance for animals. Ultraviolet rays improve the functioning of the respiratory and circulatory organs, oxygen supply to tissues. They also cause a general stimulating effect due to the expansion of blood vessels in the skin. At the same time, hair growth increases, the function of the sweat and sebaceous glands is activated, the stratum corneum thickens, and the epidermis thickens. In this regard, skin resistance increases, tissue growth and regeneration, and healing of wounds and ulcers are enhanced. Ultraviolet rays normalize phosphorus-calcium metabolism and promote the formation of vitamin D. Ultraviolet radiation serves as a powerful adaptogenic factor, widely used in livestock farming to preserve the health and increase the productivity of animals and poultry.

Ultraviolet rays have a bactericidal - bacteria-killing effect. Therefore, solar radiation has long been considered a powerful, reliable and free natural disinfectant of the external environment. Some forms of microbes and viruses die in direct sunlight within 10 to 15 minutes.

Of great importance in preventing light starvation is artificial ultraviolet irradiation using mercury-quartz lamps and the use of infrared radiation lamps for heating animals. The mode of their use, dosage and operating procedures must be controlled by veterinary specialists. Workers serving animals at the time of irradiation must observe appropriate safety precautions. Appropriate standards for the use of infrared and ultraviolet radiation lamps have been developed and are being used.

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It is no coincidence that we begin the review with this environmental factor. Radiant energy from the sun, or solar radiation, is the main source of heat and life on our planet. Only thanks to this, in the distant past on Earth, organic matter could have arisen and, in the process of evolution, reached those degrees of perfection that we observe in nature at the present time. The main properties of radiant energy as an environmental factor are determined by wavelength. On this basis, within the entire light spectrum, visible light, ultraviolet and infrared parts are distinguished (Fig. 10). Ultraviolet rays have a chemical effect on living organisms, while infrared rays have a thermal effect.

Rice. 10. Spectra of solar radiation c. various conditions (after: Odum, 1975).
1 - not changed by the atmosphere; 2 - at sea level on a clear day; 3 - passed through continuous clouds; 4 - passed through the vegetation canopy.

The main parameters of the environmental impact of this factor include the following: 1) photoperiodism - a natural change in light and dark time of day (in hours); 2) lighting intensity (in lux); 3) voltage of direct and scattered radiation (in calories per unit surface per unit time); 4) chemical action of light energy (wavelength).

The sun continuously emits enormous amounts of radiant energy. Its power, or radiation intensity, at the upper limit of the atmosphere ranges from 1.98 to 2.0 cal/cm 2 -min. This indicator is called the solar constant. However, the solar constant, apparently, can vary somewhat. It is noted that in recent years the brightness of the Sun has increased by approximately 2%. As it approaches the Earth's surface, solar energy undergoes profound transformations. Most of it is retained by the atmosphere. Further, vegetation gets in the way of the light waves, and if it is a multi-tiered closed tree plantation, then a very small part of the initial solar energy reaches the soil surface. Under the canopy of a dense beech forest, this amount is 20-25 times less than in the open. But the point is not only a sharp decrease in the amount of light, but also that in the process of penetrating deep into the forest, the spectral composition of the light changes. Consequently, it undergoes qualitative changes that are very significant for plants and animals.

Speaking about the ecological significance of light, it must be emphasized that the most important thing here is its role in the photosynthesis of green plants, because the result is the creation of organic matter, plant biomass. The latter represents the primary biological production, on the use and transformation of which everything else living on Earth depends. The intensity of photosynthesis varies greatly in different geographical areas and depends on the season of the year, as well as on local environmental conditions. Additional lighting can significantly increase the growth of even tree and shrub species, not to mention herbaceous plants. I. I. Nikitin germinated acorns for 10 days under continuous light, then 5 months. I grew seedlings in light with a brightness of 4 thousand lux. As a result, the oak trees reached a height of 2.1 m. After transplanting into the ground, the 8-year-old experimental oak tree gave an annual increase in height of 82 cm, while the control trees - only 18 cm.

It is noteworthy that although the vital activity and productivity of animals are in direct (for phytophages) or indirect (for zoophages) dependence on the primary production of plants, nevertheless, the connection between the latter and animals is far from one-sided. It has been established that phytophagous animals, such as moose, by eating green plant matter and damaging photosynthetic organs, are capable of
significantly reduce the intensity of photosynthesis and plant productivity. Thus, in the Central Chernozem Reserve (Kursk region), moose ate only 1-2% of the phytomass of young oak forests, but their productivity fell by 46%. Thus, in the system of food plant - phytophage, there is both direct and feedback.

Photoperiodism plays a huge role in the life of all living beings. As this factor is studied, it becomes clear that the photoperiodic reaction underlies many biological phenomena, being a direct factor determining them or performing signaling functions. The outstanding importance of the photoperiodic reaction is largely due to its astronomical origin and, therefore, a high degree of stability, which, for example, cannot be said about the temperature of the environment, which is also extremely important, but extremely unstable.

The very fact of dividing animals into two large groups according to the time of activity - daytime and night - clearly indicates their deep dependence on photoperiodic conditions. The same is evidenced by the pattern established in 1920 by American scientists W. Garner and G. Allard, according to which plants, in relation to light and temperature, are divided into long- and short-day species. Later it was found that a similar photoperiodic reaction is also characteristic of animals and, therefore, is of a general ecological nature.

The regular change in the length of daylight hours over the seasons determines the time of onset of diapause for numerous species of insects and other arthropods, in particular mites. Through subtle experiments, A. S. Danilevsky and his colleagues proved that diapause is stimulated precisely by the shortening of the day, and not by a decrease in air temperature, as previously thought (Fig. 11). Accordingly, the natural increase in the duration of daylight hours in the spring serves as a clear signal for the termination of the diapause state. At the same time, species populations living at different latitudes differ in specific photoperiodic requirements. For example, for the dock butterfly (A crony eta rumicis), in Abkhazia a day length of at least 14 hours 30 minutes is required, in the Belgorod region - 16 hours 30 minutes, in the Vitebsk region - 18 hours and near Leningrad - 19 hours. In other words, With every 5° latitude moving north, the length of day required to exit diapause in this species lengthens by about an hour and a half.

Rice. 11. Photoperiodic reaction of the long-day type - the cabbage butterfly (1) and the short-day type - the silkworm (2) (after: Danilevsky, 1961).

Thus, photoperiodism is a major factor in the seasonal activity of arthropods. Moreover, similar studies by botanists have shown that many phenomena in the seasonal life of plants, the dynamics of their growth and development also relate to photoperiodic reactions. For example, the photoperiodic factor serves as a signal for early preparation of plants for winter, regardless of weather conditions. All this makes photoperiodism a very significant factor when introducing agricultural plants into new areas, when cultivating them in greenhouses, etc.

Finally, a comparison of the results of experiments on the photoperiodism of phytophagous insects and their food plants revealed a deep interdependence between them. Both respond to the influence of the same environmental factor in a similar way; therefore, their trophic connections have a deep ecological and physiological basis.

The study of photoperiodic reactions of higher vertebrates also brought extremely interesting results. Thus, fur-bearing animals develop increasingly thick and luxuriant hair in the fall. In winter, it reaches its greatest development and maximum thermal insulating properties. These protective functions of the fur are enhanced by the thick layer of fat that forms under the skin in late summer and fall. In winter, the mentioned morphophysiological adaptations function fully. It has long been believed that the main factor determining the seasonal development of fur and fat is air temperature, its drop in the autumn-winter months. However, experiments have demonstrated that the triggering mechanism for this process is associated not so much with temperature as with photoperiodism. In a laboratory vivarium and even on a fur farm, you can place American minks or other animals in cages with controlled lighting and, starting in mid-summer, artificially reduce daylight hours. As a result, the molting process in experimental animals begins much earlier than in nature, will proceed more intensely and, accordingly, will end not by winter, but at the beginning of autumn.

The photoperiodic basis also underlies the most important seasonal phenomenon in the life of migratory birds - their migration and the closely related processes of molting plumage, accumulation of fat under the skin and on internal organs, etc. Of course, all of these are adaptations to endure unfavorable temperature and feeding conditions by “ avoiding" them. However, in this case, the main signaling role is played not by changes in temperature, but by light conditions - a reduction in the length of the day, which can be proven through experiments. In the laboratory, acting on the photoperiodic response of birds, it is not too difficult to bring them into a specific pre-migratory state, and then into migratory excitement, although the temperature conditions will remain stable.

It turns out that the cyclical nature of animal sexual activity and the cyclical nature of their reproduction are also photoperiodic. Perhaps this is especially surprising, since the biology of reproduction belongs to the properties of the organism that are most finely formed and have the most complex coordination of relationships.

Experiments on many species of birds and mammals have proven that by increasing the duration of daylight hours, it is possible to activate the gonads (Fig. 12), bring animals into a state of sexual arousal and achieve productive mating even in the autumn-winter months, if, of course, there is a positive reaction to light both sexes will find the impact. Meanwhile, females in some species (for example, sparrows) in this regard turn out to be much more inert than males and require additional ethological stimulation.

Rice. 12. The influence of light on the development of gonads in male and female house sparrows killed after being kept under different conditions (after: Polikarpova, 1941).
a - from freedom on January 31; b - from a room temperature chamber on January 29; c - from a chamber with additional light on January 28.

Some mammals - sable, marten, a number of other species of mustelids, as well as roe deer - have an interesting feature of reproductive biology. In them, the fertilized egg is not first implanted into the uterine wall, but<в течение длительного времени находится в состоянии покоя, так называемой латентной стадии. У соболя эта стадия продолжается несколько месяцев и лишь приблизительно за полтора месяца до рождения щенков происходит имплантация яйца и очень быстрое эмбриональное развитие. Таким образом, беременность распадается как бы на длительный период предбеременности, или латентный, и короткий, порядка 35-45 дней, период вынашивания, т. е. собственно эмбрионального развития. Благодаря этому замечательному приспособлению животные получают возможность с минимальными энергетическими затратами переживать тяжелое зимнее время. Оказывается, что продолжительность латентного периода также регулируется фотопериодической реакцией и, если воспользоваться последней, может быть существенно сокращена.

The influence of the ratio of periods of light and darkness and changes in light intensity throughout the day on the activity of animals is very large. For example, diurnal birds awaken at dawn at a “waking illumination” of a certain intensity, depending on the height of the sun relative to the horizon. The onset of proper “wake-up illumination” serves as a signal that stimulates the birds to become more active. Blackbirds begin to show signs of life at 0.1 lux, when the forest is still almost completely dark; The cuckoo requires 1 lux to awaken, the black-headed warbler - 4, the chaffinch - 12, the house sparrow - 20 lux. In accordance with this, when the weather is good, birds in a given area wake up at a certain time and in a certain order, which suggests the existence of a “bird clock”. For example, in the forestry farm "Forest on Vorskla" of the Belgorod region in May-June, the first voices of birds are heard on average at the following times: nightingale - at 2 hours 31 minutes, blackbirds and songbirds - 2 hours 31 minutes, cuckoo - 3 hours 00 minutes, black-headed warbler - 3 hours 30 minutes, great tit - 3 hours 36 minutes, tree sparrow - 3 hours 50 minutes.

Daily changes in light conditions have a profound impact on the life of plants, and above all on the rhythm and intensity of photosynthesis, which stops in the dark hours of the day, in bad weather and in winter (Fig. 13).

Finally, solar energy can play a very important role as a source of heat, affecting living things directly or profoundly affecting their environment on a local or global scale.

In general, from the above fragmentary information it is clear that the light factor plays an extremely important and versatile role in the life of organisms.

Rice. 13. Dependence of photosynthesis on light energy in different plant populations (after: Odum, 1975).
1 - trees in the forest; 2 - leaves illuminated by the sun; 3 - shaded leaves.

Ionizing radiation affects the body from both external and internal sources of radiation (in the case of penetration of radioactive substances into the body with food, water, air or through the skin). Possible combined effects of external and internal radiation.

The damaging effect of various types of radioactive rays depends on their penetrating activity and, therefore, on the ionization density in tissues. The shorter the beam path, the greater the ionization density and the stronger the damaging effect (Table 7).

However, physically identical amounts of absorbed energy often produce different biological effects depending on the type of radiant energy. Therefore, to assess the degree of damaging effects of ionizing radiation on biological objects, the coefficient of relative biological effectiveness (RBE) is used.

As can be seen from table. 8, the damaging effect of alpha rays, neutrons and protons is 10 times greater than that of x-rays, the biological effect of which is conventionally taken as 1. However, it should be remembered that these coefficients are conditional. Much depends on the choice of indicator that is taken to compare biological effectiveness. For example, RBE can be determined by the percentage of mortality, by the degree of hematogenous changes, by the sterilizing effect on the gonads, etc.

The body's response to the action of ionizing radiation depends on the received dose of radiation, the duration of action and the general condition of the irradiated body (Table 9).

For humans, the absolute lethal dose for a single exposure is about 600 rubles.

Duration of exposure has some significance in the development of radioactive damage. With short-term exposure, measured in seconds, the degree of damaging effect decreases somewhat. When exposed to the same dose of radiation, but lasting several tens of minutes, the damaging effect increases. Fractionated action reduces mortality. The total dose of multiple exposures can significantly exceed a single fatal dose.

Individual and species reactivity of the body is also of great importance in determining the severity of radioactive damage. In animal experiments, wide limits of individual sensitivity are noted - some dogs survive with a single irradiation of 600 r, while others die from 275 r. Young and pregnant animals are more sensitive to ionizing radiation. Old animals are also less resistant due to weakening of their recovery processes.

Mechanisms of pathogenic action of ionizing radiation. In the mechanism of radiation damage to the human and animal body, three important stages can be distinguished:

• a) the primary effect of radioactive radiation;
• b) the effect of radiation on cells;
• c) the effect of radiation on the whole organism.

Mechanism of primary action of ionizing radiation determined by physical, physicochemical and chemical processes that occur in any biological substrate under the influence of radiation.

Physical processes - ionizing radiation, having high energy, knocks out electrons from atoms and molecules on its way or causes them to move. This leads, within a negligibly short time (10-16 seconds), to ionization and the formation of excited atoms and molecules. Physicochemical processes consist in the fact that ionized and excited atoms and molecules, having great reactivity, cause the formation of free radicals. In living structures, water undergoes ionization most quickly.

Ionization is accompanied by the phenomena of recombination of the resulting particles. It is especially pronounced under the influence of such types of radiation that have a high ionization density (alpha rays, neutrons). In the process of water radiation, the following free atoms and radicals arise: atomic hydrogen (H +), hydroxyl (OH +), hydroperoxide (HO 2) and hydrogen peroxide (H 2 O 2).

The effect of ionizing radiation on substances dissolved in water is mainly due to the products of water radiolysis. Thus, the high radiostability of substances in a frozen state or enzymes in a dried powder state is known.

The ionization process also affects macromolecules. The absorbed energy can migrate throughout the macromolecule, being realized in its most vulnerable places. In proteins, these places can be SH groups, in DNA - chromophore groups of thymine, in lipids - unsaturated bonds.

Effect of radiation on cells arises as a result of the interaction of radicals of proteins, nucleic acids and lipids with water, oxygen, hydrogen, etc., when, as a result of all these processes, organic peroxides are formed and fast oxidation reactions occur. Many altered molecules accumulate, as a result of which the initial radiation effect is multiplied. All this is reflected primarily in the structure of biological membranes, their sorption properties change and permeability increases (including the membranes of lysosomes and mitochondria). Changes in lysosome membranes lead to the release and activation of DNase, RNase, cathepsins, phosphatase, muconblisaccharide hydrolysis enzymes and a number of other enzymes.

The released hydrolytic enzymes can, by simple diffusion, reach any cell organelle into which they easily penetrate due to increased membrane permeability. Under the influence of these enzymes, further decomposition of the macromolecular components of the cell occurs, including nucleic acids and proteins. The uncoupling of oxidative phosphorylation as a result of the release of a number of enzymes from mitochondria, in turn, leads to inhibition of ATP synthesis, and hence to disruption of protein biosynthesis.

Thus, the basis of radiation damage to cells is a violation of the ultrastructures of cellular organelles and associated metabolic changes. In addition, ionizing radiation causes the formation in the tissues of the body of a whole complex of toxic products that enhance the radiation effect - the so-called radiotoxins. Among them, the most active are the oxidation products of lipoids - peroxides, epoxides, aldehydes and ketones. Formed immediately after irradiation, lipid radiotoxins stimulate the formation of other biologically active substances - quinones, choline, histamine - and cause increased protein breakdown. When administered to non-irradiated animals, lipid radiotoxins have effects reminiscent of radiation injury.

At sufficiently high radiation doses, changes in cells and tissues are determined mainly by the development of degenerative-destructive processes and structural changes in the chromosomal apparatus, which leads to cell death during mitosis or the emergence of non-viable cell progeny. Inhibition of cell mitotic activity is one of the specific manifestations of the biological effect of ionizing radiation.

Ionizing radiation affects cells the more strongly, the greater their reproductive capacity, the longer the mitotic process, the younger and less differentiated the cells. Based on the morphological signs of susceptibility, organs and tissues are distributed in the following descending order: lymphoid organs (lymph nodes, spleen, thymus, lymphoid tissue of other organs), bone marrow, testes, ovaries, mucous membrane of the gastrointestinal tract. The skin with appendages, cartilage, growing bones, and vascular endothelium are even less affected. Parenchymal organs are highly radioresistant: liver, adrenal glands, kidneys, salivary glands, lungs.

The degree of radiation damage to cells of the same type depends on a number of factors:

• 1) degree of differentiation - embryonic and undifferentiated cells are affected to a greater extent than the differentiated cells formed from them;
• 2) metabolism - increased intensity of cellular metabolism is accompanied by increased radiosensitivity;
• 3) mitotic activity - actively dividing cells, as a rule, are more sensitive than non-dividing ones. The cell nucleus is more sensitive to radiation than the cytoplasm;
• 4) stages of mitosis - the sensitivity of cells is highest at the stage of prophase and metaphase.

Radiosensitivity changes dramatically at different stages of phylogenetic development. The susceptibility of animals to radiation decreases in the following order: embryo, fetus, young animal, adult organism.

The effect of ionizing radiation on the body as a whole. The pathogenic effect of ionizing radiation is generally determined by both the direct damaging effect on the cells and tissues of the body, and irritation of the nervous system and the resulting general reactions of the body, referred to as radiation sickness.

Radiation sickness. According to the flow they distinguish acute and chronic radiation sickness. Acute radiation sickness can occur in mild, moderate and severe forms. There are four periods during its course.

First period - initial (primary reactions), observed immediately after irradiation, lasts from several hours to 1-2 days. A sign of radiation injury during this period is a delay in mitotic activity in hematopoietic cells. During this period, metabolic processes intensify and the functions of the main organs and systems increase.

The second period is latent, hidden (period of apparent well-being), characterized by changes in the patient’s blood associated with the beginning inhibition of hematopoiesis. The duration of this period depends on the absorbed dose. So, at doses of 20-100 rads, this period may end the disease. At a dose of 150-200 rads, the latent period can last several weeks, at 300-500 rads - only a few days, and at a dose above 500 rads, the latent period lasts only a few hours.

The third period - pronounced phenomena, or the height of the disease . In mild cases it lasts several days, in severe cases it lasts 2-3 weeks. This period is characterized by hemorrhages in the internal organs, a sharp suppression of hematopoiesis (Fig. 5), increased permeability of cell membranes, and suppressed immunity. It is during this period that death occurs. The causes of death may be bleeding, associated infection and other complications.

The fourth period is the period of exodus or restoration .

Chronic radiation sickness occurs with weak, long-term irradiation of the body, and can also be the outcome of acute radiation sickness. During chronic radiation sickness, three periods are distinguished: the period of early changes, the development of complications and the period of severe, irreversible changes with a fatal outcome.

Mechanism of development of radiation sickness Along with direct damage to cells, it is determined mainly by the body’s reaction from the nervous, endocrine and connective tissue systems to damaging radioactive radiation.

The reaction of the nervous system can be observed in all phases of the development of radiation sickness. At the beginning of its development, when ionization of water and biosubstrates of the body occurs, the receptors of the nervous system react to changes in the internal environment of the body, leading to excitation of all parts of the nervous system.

Disorders of the function of the central nervous system are manifested in violations of conditioned reflex connections, weakening of the process of internal inhibition. Functional changes in the cerebral cortex at different periods of irradiation are associated with an increase in impulses flowing into the higher parts of the nervous system through the reticular formation. The functions of all subcortical centers also change. Thus, a manifestation of damage to the vegetative centers is a violation of thermoregulation, regulation of vascular tone, and heart rate in the irradiated organism. Thus, during radiation diseases, the earliest and most intense functional changes are detected in the nervous system, and structural disorders in it are not as pronounced as, for example, in the bone marrow (P. D. Gorizontov).

Endocrine disorders also play a significant role in the development of radiation sickness. The functions of all endocrine glands are disrupted to one degree or another under the influence of ionizing radiation. The most pronounced changes are observed in the gonads, pituitary gland and adrenal glands. These changes depend on the dose of radiation and can manifest themselves as either an increase in secretion or a decrease in it. Of great importance, apparently, is the disruption of the usual consistency in the secretion of various endocrine glands.

Radiation damage to the gonads during chronic exposure to penetrating radiation can occur very early - before the appearance of clinical symptoms of radiation sickness. Changes that occur in the gonads lead to sterility, a decrease in offspring, and an increase in stillbirth.

Dysfunction of the pituitary gland, accompanied by changes in the secretion of a number of triple hormones, leads to a variety of secondary consequences due to dysfunction of the corresponding glands. Particularly important is the insufficiency of the adrenal glands, which sharply reduces the body's reactivity and resistance to all kinds of damaging environmental influences.

Long-term effects of radiation. Among the long-term consequences of radiation, the most studied (except for chronic radiation sickness) are a reduction in average life expectancy, the development of cataracts, disorders of embryonic development, and the occurrence of malignant tumors.

Irradiation increases the number of malignant tumors and accelerates their occurrence (in an experiment). Most often, tumors of hematopoietic tissue (leukemia), breast, skin, liver, and thyroid gland are formed.

Tumors can arise from both general and local irradiation.

Exposure to ionizing radiation is also used as a powerful antitumor agent. Irradiation is always carried out locally. The exposure mode is selected in such a way that most of the radiation energy is absorbed in the tumor and near it. The effect of radio radiation is most effective in the case of tumors with increased mitotic activity and reduced radioresistance.

Sun rays

Ultraviolet rays (UVR). Ultraviolet rays (wavelength from 1880 to 3800 A) penetrate only into the most superficial layers of the skin and have a biological and pathological effect on the body.

The general biological effect of ultraviolet rays on humans is expressed in three ways:

1. Skin reaction - mid-wave ultraviolet rays (2800-3150 A) cause erythema. Erythema occurs as a result of the formation of histamine, which is a strong vasodilator, at the site of irradiation. It has sharply defined boundaries, occurs after a certain period of time (from tens of minutes to several hours) and, as a rule, goes into pigmentation - tanning with the formation and deposition of melanin pigment in the skin. Tanning is caused predominantly by long-wave ultraviolet rays (3150-3800 A).

• 2. Under the influence of ultraviolet rays in the skin, vitamin D 3 is formed photochemically from provitamin 7-dehydrocholesterol. The minimum amount of ultraviolet rays required for this is 1/8-1/10 of the erythemal dose per day.

• 3. The bactericidal effect of ultraviolet rays is most pronounced within the wavelength range from 2000 to 2800 A (short-wave ultraviolet). The bactericidal effect is also accompanied by stimulation of immunological reactivity: the production of antibodies is enhanced and the complementary activity of blood serum increases.

Ultraviolet rays of the shortest range (less than 2000 A) have an ozonizing effect (vacuum ultraviolet).

Pathogenic effect of UFL manifests itself when the body is exposed to excessive radiation or in the presence of increased sensitivity (photosensitization).

Sunburns strictly at the site of irradiation occur due to the chemical action of UV rays - excessive formation of histamine and other biologically active substances in irradiated tissues and their subsequent toxic effects, both local and general.

Eye damage UVL - photoophthalmia - occurs more often in the absence of protection of the sclera of the eyes in conditions of increased radiation (for electric welders, when working in light therapy rooms, in arctic and high mountain regions, etc.); appears after 2-6 hours, is expressed in pain in the eyes, hyperemia, swelling of the conjunctiva and eyelids, decreased visual acuity. A general reaction of the body is also observed - headache, fatigue, insomnia, tachycardia. Usually these symptoms disappear after 5-6 days.

General action UVL can also manifest itself as general reactions with the leading role of local symptoms, as well as as an independent reaction to general ultraviolet radiation - sunstroke, where the leading factor is a violation of the general condition of the body, primarily the functions of the central nervous system and circulatory organs.

In the mechanism of the general pathogenic action of UFL, two pathways are of greatest importance: humoral and neurogenic .

Humoral mechanisms . At the site of irradiation, under the influence of UV rays, toxic products are formed - histamine, acetylcholine, irradiated cholesterol, ergosterol, protein-lipoid complexes, which have a toxic effect on the capillary wall at the site of their formation, on nerve cells and sensitive nerve endings due to absorption into the general bloodstream.

Intense irradiation of the skin with UV rays causes hemolysis of red blood cells - the so-called photohemolysis, which is especially enhanced in the presence of photosensitizers. Photosensitizers - some dyes (eosin, fluorescein), porphyrins, lecithin, cholesterol - enhance the damaging effects of UV rays.

Some people with impaired porphyrin metabolism (porphyria) develop burns and a state of severe collapse due to poisoning by toxic products of irradiated porphyrin even with minor solar irradiation.

Neurogenic mechanisms . Possible reflex excitation of some vegetative centers (vasomotor, vagal, thermoregulation centers) through skin receptors irritated by chemicals at the site of their formation.

It is also possible that these same toxic products have a centrogenic effect on vital nerve centers as a result of absorption into the bloodstream, lymph and cerebrospinal fluid - hence circulatory disorders such as collapse, which can sometimes result in death (sunstroke).

Blastomogenic effect A person can be exposed to UV rays with a wavelength from 2900 to 3841 A with prolonged exposure. In animals, tumors can be caused by radiation with a wider wavelength range. The absorption of UV rays by the upper layers of the skin determines to a certain extent the localization of human tumors developing under their influence, for example, squamous and basal cell skin cancer. In animals with thinner skin, sarcomas occur in a significant percentage of cases. In humans, tumors develop on open, unprotected areas of the body, and in experimental animals - on parts of the body that are devoid of hair.

The incidence of skin tumors increases with the amount of energy absorbed. Thus, it is estimated that in the United States between 42° and 30° north latitude, the incidence of skin cancer doubles with every 4° approach to the equator. Skin cancer caused by UV rays occurs after a long latent period. The appearance of cancer is preceded by long-term destructive and inflammatory changes in the skin, called solar keratosis.

The mechanism of the blastomogenic effect of ultraviolet rays is far from clear. There are two possible ways of doing this:

• a) UFL, like radioactive radiation, have mutagenic properties (see “The role of heredity, constitution and age in pathology”);
• b) under the influence of UV rays, some carcinogenic substances can form in the skin.

Violet rays (3800-4500 A) can have a chemical effect on the body, similar to ultraviolet radiation, but much less pronounced.

Visible rays of the solar spectrum with a wavelength of 5000-7000 A they do not have a significant damaging effect, since they are mainly absorbed by the skin and do not penetrate deep into the body.

Through the eye, an organ specialized for the perception of solar spectrum rays ranging from 4000 to 7600 A, light stimulation can affect the entire body. Irritation of the visual receptors by light rays is transmitted, in addition to the visual centers, to the autonomic centers of the hypothalamus and leads them to a state of weak excitation, which in turn contributes to increased oxidative processes, increased blood pressure and even the emergence of some euphoria (on a bright, sunny day people are more smiling and more sociable than on gloomy, cloudy days).

The natural rhythm of lighting determines the daily rhythm of animal and human activity, the rhythm of a number of physiological processes, closely connected by reflex and conditioned reflex mechanisms with the rhythm of day and night, and the rhythm of seasonal fluctuations in illumination. Disturbances in the normal rhythm of physiological functions associated with the rhythm of the natural cycle of day and night, in some cases lead to the development of painful conditions (neuroses), the treatment of which requires the restoration of the normal rhythm of light stimulation. Such violations may be the result of improper work and living conditions, 24-hour day and 24-hour night in the Arctic Circle, etc.

Infrared rays. Infrared rays have a mainly thermal effect on the body. Rays with wavelengths from 7600 to 14,000 A have great penetrating power and heat tissues as if from the inside. Rays with a wavelength of more than 14,000 A are absorbed by superficial tissues and can produce a burning effect.

An increase in temperature as a result of tissue absorption of the energy of infrared rays is accompanied by an acceleration of various physicochemical and physiological reactions of the body, both local (increased vascular permeability, their expansion - passive hyperemia, exudation, etc.) and general (increased metabolism, body temperature, etc.) severe cases - violations of thermoregulation mechanisms and heat stroke) nature.

Laser radiation

A laser, or optical quantum generator, is a physical device that makes it possible to emit monochromatic beams of light of extraordinary intensity with a small angle of divergence. An unfocused laser beam has a width of 1-2 cm, and with an induced focus from 1 to 0.01 mm or less. Therefore, it is possible to concentrate enormous light energy into an area of ​​several microns and achieve very high temperatures. The energy of each laser flash can be measured in hundreds and thousands of joules. The laser beam is capable of melting diamond, steel and other materials.

There are pulsed and continuous lasers; both are used in medicine. The action of the laser beam on living tissue occurs within very short intervals (hundred-thousandths of a second), and, apparently, therefore there is no sensation of pain. The penetration depth can be adjusted using an optical system and usually reaches 20-25 mm.

The degree of absorption of laser beams depends on the color of the irradiated object. Most of all, they are absorbed by pigmented tissues, red blood cells, melanomas, etc. Laser beams destroy and melt living tissues; Tumor tissues are especially sensitive to them.

The mechanism of the damaging effect of laser beams on biological objects consists of a number of factors:

• 1) the thermal effect of the beam itself and a secondary increase in the temperature of the underlying tissues as a result of the absorption of thermal energy;
• 2) mechanical action as a result of the occurrence of elastic vibrations such as ultrasonic or even shock waves. A kind of “explosive effect” occurs due to the instantaneous transition of solid and liquid substances of the body into a gaseous state and a sharp increase in interstitial pressure (up to several tens and hundreds of atmospheres):
• 3) biological effect - toxic substances are formed in tissues and cells after exposure to a laser beam. Perhaps the progressive necrosis of cells after irradiation depends on them;
• 4) inactivation or change in the specific action of tissue enzymes.

The possibility of ionization of tissue components and the emergence of magnetic fields is allowed.

The degree and result of the impact of the laser beam depend on the characteristics of the radiation itself (type of laser, power, duration of action, radiation density, pulse frequency), the physicochemical and biological characteristics of the irradiated tissues (degree of pigmentation, blood circulation, heterogeneity of tissues, their elasticity, thermal conductivity, etc. .).

Due to their biological and physicochemical characteristics, tumor cells are more sensitive to the laser beam than healthy ones. It is in oncology that this type of radiation is so far most widely used. In addition, the laser is used for bloodless operations in surgery, ophthalmology, etc.