Regeneration sometimes physiological, reparative and pathological... The regeneration process is very close, in fact identical to the hyperplastic process (multiplication of cells and intracellular structures). They differ in that hyperplasia (hypertrophy) usually arises in connection with the need to enhance the function, and regeneration - with the "goal" of normalizing the function in the event of organ damage and loss of part of its mass. Previously, it was believed that regeneration is limited only to organ and tissue levels. Now it has become obvious that physiological and reparative regeneration is a universal phenomenon, characteristic not only of the tissue and cellular levels, but also of the intracellular, including molecular (regeneration of the damaged DNA structure). So, after the pathogenic effect and damage to DNA, its "healing" occurs, carried out by the sequential work of reparative enzymes. They "recognize" the damaged area, expand it, ie. as if they cleanse the site of damage, and then "build up" the resulting gap along the complementary intact DNA strand and "stitch" the inserted nucleotides. The most remarkable thing in the process of DNA repair is that it, as it were, in miniature repeats those main links of the regenerative process that we are used to observing when it unfolds at the tissue level - damage, enzymatic cleavage of dead tissues and cleansing of the damaged area within healthy tissues, filling the resulting defect with a newly formed tissue of the same type (complete regeneration) or connective tissue (incomplete regeneration). This indicates that with all the seemingly endless variety of processes unfolding in the body, each of them, in principle, proceeds according to some universal, common for all levels of organization, typical scheme.
Regeneration, proceeding at the molecular and ultrastructural levels, is limited to cells, and therefore it is called intracellular. Structural support of the body's adaptation to everyday environmental influences is provided by corresponding fluctuations in intensity physiological regeneration , which, in case of illness, sharply increases and takes on character reparative. Both physiological and reparative regeneration in some organs is provided by all its forms - cellular (mitosis, amitosis) and intracellular. In the same organs and systems as the central nervous system and the heart (myocardium), where cell proliferation is absent, the structural basis for the normalization of their function is exclusively intracellular regeneration. Thus, the latter is a universal form of regeneration characteristic of all organs, without exception.
Reparative regeneration can be complete, incomplete and intracellular.
Cell form regeneration is inherent in the following organs and tissues (bone, hematopoietic, loose connective, endothelium, mesothelium, mucous membranes of the gastrointestinal tract, genitourinary system, respiratory system, skin, lymphoid tissue),
To organs and tissues where prevails intracellular form of regeneration, include the myocardium and nerve cells.
In some organs, a cellular and intracellular form of regeneration is observed - liver, kidneys, lungs, smooth muscles, endocrine glands, pancreas, autonomic nervous system.
The morphogenesis of the reparative process consists of two phases - proliferation and differentiation... The first phase is the multiplication of young undifferentiated cells (cambial, stem or progenitor cells). By multiplying and then differentiating, they make up for the loss of highly differentiated cells. There is another point of view about the sources of regeneration. It is assumed that the source of regeneration can be highly differentiated cells of an organ, which, under conditions of a pathological process, can be rearranged, lose some of its specific organelles and at the same time acquire the ability to mitotic division with subsequent proliferation and differentiation. The outcomes of the regeneration process can be different. In some cases, reparative regeneration ends with the formation of a part identical to the deceased - then they speak of complete regeneration or restitution. In others, incomplete regeneration (substitution) occurs. In the area of damage, not tissue specific to a given organ is formed, but a connective tissue, which subsequently undergoes scarring. In this case, the remaining structures compensatory increase in their mass, i.e. hypertrophied. Regenerative hypertrophy arises, which is the expression of the essence of incomplete regeneration. Regenerative hypertrophy can be carried out in two ways - cell hyperplasia (liver, kidney, gland, lungs, spleen, etc.) and ultrastructures (cell hypertrophy - myocardium and brain neurons). Basically, those tissues in which cellular regeneration are inherent are completely regenerated, striated muscles, myocardium, and large vessels are not completely regenerated. Regeneration. Hypertrophy is observed in the liver, lungs, kidneys, endocrine glands, ANS.
Pathological regeneration- perversion of the regeneration process towards hyporegeneration or hyperregeneration, in fact, it is an incorrectly proceeding reparative regeneration. Examples of such regeneration and their reasons are:
1. Tissues have not lost their regenerative capacity, but according to physical and biochemical conditions, regeneration takes an excessive character, resulting in tumor-like growths and leading to functional disorders (intensive growth of granulation tissue in wounds / excessive granulation /, keloid scars after burns, amputation neuromas).
2. Loss of tissues of the usual, adequate rates of regeneration (for example, with exhaustion, vitamin deficiencies, diabetes) - long-term non-healing wounds, pseudoarthrosis, epithelial metaplasia - in the focus of chronic inflammation).
3. Regeneration has a qualitatively new character in relation to the tissues that have arisen, this is associated with the functional inferiority of the regenerate / for example, the formation of false lobules in liver cirrhosis /, and sometimes its transition into a new qualitative process - a tumor.
Regeneration carried out under the influence of various regulatory mechanisms:
1) humoral (hormones, poetic factors, growth factor, keylons)
2) immunological (the fact of transfer of "regenerative information" by lymphocytes, which stimulates the proliferative activity of cells of various internal organs, has been established
3) nervous and
4) functional (dosed functional load).
The efficiency of regeneration processes is largely determined by the conditions in which it takes place. The general state of the organism is of great importance in this respect. Exhaustion, hypovitaminosis, disturbance of innervation, etc. has a significant effect on the course of reparative regeneration, inhibiting it and converting it into pathological one. A significant influence is exerted by the degree of functional load, the correct dosage of which promotes regeneration (restoration of bone tissue in fractures). The rate of reparative regeneration is, to a certain extent, determined by age, constitution, metabolism, and nutrition. Local factors are also important - the state of innervation, blood and lymph circulation, the nature of the pathological process, the proliferative activity of cells.
Healing wounds occurs according to the laws of reparative regeneration. Depending on the depth of the defect, the type of tissue and treatment methods, there are 4 types of wound healing.
1. Direct closure of the defect of the epithelial integument, in which the creeping of epithelial cells onto the surface of the defect from the area of the edges of the damage is noted.
2. Healing under a scab occurs in small defects, on the surface of which a crust (scab) forms, under which epithelial cells grow within 3-5 days, after which the crust disappears.
3. Primary tension.
4. Secondary tension.
Healing by primary intention occurs in the area of treated and sutured skin wounds or small defects of organs and tissues, in which, due to weak tissue trauma and small microbial invasion, dystrophic and necrobotic changes in cells and fibers are minimal even at the ultrastructural level. The primary reaction of mast cells and microcirculation vessels is relatively weak, therefore, the exudation is moderate and has a serous character, the neutrophilic and macrophage stages of the inflammatory cellular response are weakened due to the low concentration of mediators that determine the chemotaxis of these cells. This leads to a rapid cleansing of the wound and the transition to the proliferative phase - the appearance of fibroblasts, the formation of capillaries, then argyrophilic and collagen fibers. Granulation tissue, which is poorly expressed at initial tension, matures quickly (10-15 days). The surface of the defect is epithelized and a delicate scar forms at the site of the wound.
Healing by secondary intention occurs with large and deep, open defects, with active microbial invasion through suppuration. On the border with the dead tissue, demarcation purulent inflammation develops. Within 5-6 days, the necrotic masses are rejected (secondary cleaning of the wound) and granulation tissue begins to form at the edges of the wound. Granulation tissue, gradually filling the wound defect, has pronounced signs of inflammation and a complex six-layer structure described by N.N. Anichkov:
1.surface leukocyte-necrotic layer
2.Surface layer of vascular loops
3.Layer of vertical vessels
4. maturing layer
5.layer of horizontally located fibroblasts
6. fibrous layer.
Atrophy(a-exception, trophe-food) – a decrease in the volume of cells, tissues, organs with a decrease or termination of their function. A decrease in the volume of tissues and organs occurs with atrophy due to parenchymal elements. Atrophy must be distinguished from hypoplasia- congenital underdevelopment of organs and tissues.
Atrophy is usually divided into physiological and pathological, local and general.
Physiological atrophy occurs throughout a person's life. So, with age, atrophy: the thymus gland, sex glands, bones, intervertebral cartilage.
Pathological atrophy occurs with circulatory disorders, nervous regulation, intoxication, the action of biological, physical and chemical factors, and malnutrition.
General atrophy manifests itself exhaustion... At the same time, there is a pronounced decrease in body weight, dryness and flabbiness of the skin. Subcutaneous fat is practically absent. There is also no fatty tissue in the greater and lesser omentum, around the kidneys. Its preserved areas are brown-brown due to the accumulation of lipochromes. In the liver and myocardium, manifestations of brown atrophy with the accumulation of lipofuscin in their cells. Internal organs, endocrine glands are reduced in size.
There are the following types of depletion: 1. Nutritional depletion, which develops during fasting or impaired assimilation of food; 2. exhaustion with cancer cachexia / most often with cancer of the stomach and other parts of the gastrointestinal tract /; 3. exhaustion with pituitary cachexia (Simmonds disease with destruction of the adenohypophysis); 4. exhaustion in cerebral cachexia, which occurs in senile forms of dementia, Alzheimer's and Pick's diseases, due to the involvement of the hypothalamus in the process; 5.exhaustion in other diseases, more often in chronic infections: tuberculosis, chronic dysentery, brucellosis, etc.
There are the following types of local atrophy:
1. Dysfunctional atrophy (from inaction) resulting from a decrease in organ function, due to its lack of demand. An example of such atrophy is muscle atrophy in fractures of bones, bone tissue of the alveolar processes of the jaws after tooth extraction.
2. Atrophy due to insufficient blood supply - occurs as a result of narrowing of the lumen of the vessels that supply blood to this organ or tissue. Examples are: renal atrophy due to hyalinosis of arterioles in hypertension, cerebral atrophy in atherosclerosis of the cerebral arteries.
4. Neurotic atrophy occurs when tissue innervation disorders in diseases and injuries of the central nervous system and peripheral nerves: atrophy of the soft tissues of the hand with damage to the brachial nerve, atrophy of the striated muscles in people who have had poliomyelitis.
1. Atrophy from the action of chemical and physical factors. So, radiation causes atrophy of the bone marrow and gonads. Long-term use of ACTH causes atrophy of the adrenal cortex, insulin - atrophy of the pancreatic islets of Langerhans.
Atrophied organs, when examined with the naked eye, are usually reduced. Their surface is smooth or grainy. When lipofuscin accumulates in an atrophied organ, they speak of brown atrophy, which takes place in the myocardium and liver.
Atrophy in the early stages of development is a reversible process and if its cause is eliminated, organ function can be restored.
Regeneration (from Latin regeneratio - rebirth) is a process of renewal of all functioning structures of the body (biomolecules, cellular organelles, cells, tissues, organs and the whole organism) and is a manifestation of the most important attribute of life - self-renewal. Thus, physiological regeneration at the cellular and tissue level is the renewal of the epidermis, hair, nails, cornea, epithelium of the intestinal mucosa, peripheral blood cells, etc. According to the isotope method, the composition of the atoms of the human body is renewed by 98% during the year. In this case, the cells of the gastric mucosa are renewed in 5 days, fat cells in 3 weeks, skin cells in 5 weeks, and skeletal cells in 3 months.
Regeneration in the broadest sense of the word is a normal renewal of organs and tissues, and restoration of what was lost, and elimination of damage, and, finally, reconstruction (reconstruction of an organ).
The body has two main strategies for tissue replacement and self-renewal (regeneration). The first way is that differentiated cells are replaced as a result of their formation of new ones from regional stem cells. An example of this category is hematopoietic stem cells. The second way is that tissue regeneration occurs due to differentiated cells, but retaining the ability to divide: for example, hepatocytes, musculoskeletal and endothelial cells.
Regeneration phases: proliferation (mitosis, an increase in the number of undifferentiated cells), differentiation (structural and functional specialization of cells) and morphogenesis.
Types and forms of regeneration
1. Cellular regeneration- This is cell renewal as a result of mitosis of undifferentiated or poorly differentiated cells.
For the normal course of regeneration processes, not only stem cells play a decisive role, but also other cellular sources, the specific activation of which is carried out by biologically active substances (hormones, prostaglandins, poets, specific growth factors):
- activation of reserve cells that stopped at an early stage of their differentiation and do not participate in the development process before receiving a stimulus for regeneration
Temporary dedifferentiation of cells in response to a regenerative stimulus, when differentiated cells lose signs of specialization and then again differentiate into the same cell type
Metaplasia is transformation into cells of a different type: for example, a chondrocyte is transformed into a myocyte or vice versa (an organopreparation as an adequate determinant stimulus of physiological cell metaplasia).
2. Intracellular regeneration- renewal of membranes, preserved organelles, or an increase in their number (hyperplasia) and size (hypertrophy).
3. Biochemical regeneration- renewal of the biomolecular composition of the cell, its organelles, nucleus, cytoplasm (for example, peptides, growth factors, collagen, hormones, etc.). The intracellular form of regeneration is universal, since it is characteristic of all organs and tissues.
Reparative regeneration(from Lat. reparatio - recovery) occurs after damage to tissue or organ (for example, mechanical injury, surgery, the action of poisons, burns, frostbite, radiation exposure, etc.). Reparative regeneration is based on the same mechanisms that are inherent in physiological regeneration.
The ability to repair internal organs is very high: liver, ovary, intestinal mucosa, etc. An example is the liver, in which the source of regeneration is practically inexhaustible, as evidenced by the well-known experimental data obtained in animals: with 12-fold removal of a third of the liver during the year in rats by the end of the year, under the influence of organopreparations, the liver restored its normal size.
Reparative regeneration of such tissues as muscle and skeletal has certain features. For muscle repair, it is important to preserve its small stumps at both ends, and for bone regeneration, the periosteum is necessary. The repair inducers are biologically active substances released during tissue damage. In addition, individual fragments of the same damaged tissue can be inducers: complete replacement of the defect in the bones of the skull can be obtained after the introduction of bone sawdust into it.
Reparative regeneration can take two forms.
1. Complete regeneration - the area of necrosis is filled with tissue identical to the dead tissue, and the site of injury disappears completely. This form is typical for tissues in which regeneration proceeds predominantly in the cellular form. Full regeneration includes the restoration of intracellular structures in case of cell degeneration (for example, fatty degeneration of hepatocytes in people who abuse alcohol).
2. Incomplete regeneration - the site of necrosis is replaced by connective tissue, and the normalization of organ function occurs due to hyperplasia of the remaining surrounding cells (myocardial infarction). This method takes place in organs with predominantly intracellular regeneration.
Research Prospects for Regeneration. At present, organic preparations are being actively investigated - extracts of the contents of a living cell with all important cellular macromolecules (proteins, bioregulatory substances, growth and differentiation factors) included in it. Each tissue has a certain biochemical specificity of its cellular content. Due to this, a large number of organopreparations are produced with a targeted focus on certain tissues and organs.
In general, the direct influence of organopreparations, as standards of cell biochemistry, consists primarily in the elimination of the cellular imbalance of bioregulators of regeneration processes, on maintaining the balance of optimal concentrations of biomolecules and on maintaining chemical homeostasis, which is disturbed under conditions not only of any pathology, but also during functional changes. This leads to the restoration of mitotic activity, cell differentiation and tissue regenerative potential. Organopreparations provide the quality of the most important characteristic of the physiological regeneration process - they contribute to the appearance in the process of division and differentiation of healthy and functionally active cells that are resistant to environmental toxins, metabolites and other influences. Such cells form a specific microenvironment characteristic of this type of healthy tissue, which has a depressing effect on the existing "plus-tissue" and prevents the appearance of malignant cells.
So, the influence of organopreparations on the processes of physiological regeneration consists in the fact that, on the one hand, immature developing cells of homologous tissue (regional stem cells, etc.) stimulate normal development into mature forms, i.e. stimulate the mitotic activity of normal tissues and cell differentiation, and on the other hand, normalize cellular metabolism in homologous tissues. As a result, physiological regeneration occurs in the homologous tissue with the formation of normal cell populations with optimal metabolism, and this whole process is physiological in nature. Due to this, in case of damage to an organ (for example, skin or gastric mucosa), organopreparations provide ideal repair - healing without a scar.
It should be emphasized that the restoration of mitotic activity and cell differentiation under the influence of organopreparations is key in correcting defects and anomalies in the development of organs in children.
In conditions of pathology or accelerated aging, physiological regeneration processes also take place, but they do not have such a quality - young cells appear that are not resistant to circulating toxins, perform their functions insufficiently, are not able to resist pathogens, which creates conditions for the preservation of the pathological process in the tissue or organ, for the development of premature aging. Hence, the expediency of using organopreparations as means capable of most effectively restoring the regenerative potential and biochemical homeostasis of tissue, organ and the whole organism, and thus preventing the aging process, is clear and obvious. And this is nothing more than revitalization.
Regeneration(from Lat. regeneratio - rebirth) - the process of restoration of lost or damaged structures by the body. Regeneration supports the structure and functions of the body, its integrity. There are two types of regeneration: physiological and reparative. The restoration of organs, tissues, cells or intracellular structures after their destruction during the life of the body is called physiological regeneration. The restoration of structures after injury or the action of other damaging factors is called reparative regeneration. During regeneration, processes such as determination, differentiation, growth, integration, etc., occur, which are similar to the processes taking place in embryonic development. However, during regeneration, all of them are already a second time, i.e. in a formed organism.
Physiological regeneration is the process of renewing the functioning structures of the body. Due to physiological regeneration, structural homeostasis is maintained and the organs can constantly perform their functions. From a general biological point of view, physiological regeneration, like metabolism, is a manifestation of such an important property of life as self-renewal.
An example of physiological regeneration at the intracellular level is the processes of restoration of subcellular structures in cells of all tissues and organs. Its significance is especially great for the so-called "eternal" tissues that have lost the ability to regenerate through cell division. This primarily applies to the nervous tissue.
Examples of physiological regeneration at the cellular and tissue levels are the renewal of the epidermis of the skin, the cornea of the eye, the epithelium of the intestinal mucosa, peripheral blood cells, etc. The derivatives of the epidermis - hair and nails - are renewed. This is the so-called proliferative regeneration, i.e. replenishment of the number of cells due to their division. In many tissues, there are special cambial cells and foci of their proliferation. These are crypts in the epithelium of the small intestine, bone marrow, proliferative zones in the epithelium of the skin. The intensity of cellular renewal in the listed tissues is very high. These are the so-called "labile" fabrics. All erythrocytes of warm-blooded animals, for example, are replaced in 2-4 months, and the epithelium of the small intestine is completely replaced in 2 days. This time is required for the cell to move from the crypt to the villus, perform its function and die. The cells of organs such as the liver, kidney, adrenal gland, etc., are renewed much more slowly. These are the so-called "stable" tissues.
The intensity of proliferation is judged by the number of mitoses per 1000 counted cells. If we take into account that mitosis itself lasts on average about 1 hour, and the entire mitotic cycle in somatic cells on average lasts 22-24 hours, it becomes clear that to determine the intensity of the renewal of the cellular composition of tissues, it is necessary to count the number of mitoses within one or several days. ... It turned out that the number of dividing cells is not the same at different hours of the day. So was opened circadian rhythm of cell division, an example of which is shown in Fig. 8.23.
Rice. 8.23. Diurnal changes in the mitotic index (MI)
in the epithelium of the esophagus ( I) and cornea ( 2 ) mice.
The mitotic index is expressed in ppm (0/00), reflecting the number of mitoses
in a thousand counted cells
The daily rhythm of the number of mitoses was found not only in normal, but also in tumor tissues. It is a reflection of a more general pattern, namely the rhythm of all body functions. One of the modern areas of biology - chronobiology - studies, in particular, the mechanisms of regulation of circadian rhythms of mitotic activity, which is very important for medicine. The existence of the very daily periodicity of the number of mitoses indicates the regulation of physiological regeneration by the body. In addition to diurnal, there are lunar and annual cycles of tissue and organ renewal.
In physiological regeneration, two phases are distinguished: destructive and restorative. It is believed that the decay products of some cells stimulate the proliferation of others. Hormones play an important role in the regulation of cellular renewal.
Physiological regeneration is inherent in all types of organisms, but it proceeds especially intensively in warm-blooded vertebrates, since they generally have a very high intensity of functioning of all organs in comparison with other animals.
Reparative(from Lat. reparatio - restoration) regeneration occurs after tissue or organ damage. It is very diverse in terms of the factors causing damage, in terms of the extent of damage, in terms of recovery methods. Mechanical trauma, such as surgery, the action of toxic substances, burns, frostbite, radiation exposure, starvation, and other pathogenic agents are all damaging factors. The most widely studied regeneration after mechanical injury. The ability of some animals, such as hydra, planaria, some annelids, starfish, ascidians, etc., to restore lost organs and parts of the body has long amazed scientists. Charles Darwin, for example, considered amazing the ability of the snail to reproduce the head and the ability of the salamander to restore the eyes, tail and legs exactly in those places where they were cut off.
The amount of damage and subsequent recovery are very different. An extreme option is the restoration of the whole organism from a separate small part of it, in fact from a group of somatic cells. Among animals, such restoration is possible in sponges and coelenterates. Among plants, it is possible to develop a whole new plant even from one somatic cell, as was obtained by the example of carrots and tobacco. This type of recovery processes is accompanied by the emergence of a new morphogenetic axis of the organism and was named by B.P. Tokin "somatic embryogenesis", because in many ways it resembles embryonic development.
There are examples of the restoration of large areas of the body, consisting of a complex of organs. Examples are the regeneration of the mouth end in the hydra, the head end in the annelid worm, and the restoration of the starfish from one ray (Fig. 8.24). Regeneration of individual organs is widespread, for example, limbs in newts, tail in lizards, eyes in arthropods. Healing of the skin, wounds, damage to bones and other internal organs is a less voluminous process, but no less important for restoring the structural and functional integrity of the body. Of particular interest is the ability of embryos in the early stages of development to recover after significant loss of material. This ability was the last argument in the struggle between the adherents of preformism and epigenesis and in 1908 led G. Driesch to the concept of embryonic regulation.
Rice. 8.24. Regeneration of a complex of organs in some species of invertebrates. A - hydra; B - annelid worm; V - starfish
(for an explanation see the text)
There are several types or methods of reparative regeneration. These include epimorphosis, morphallaxis, epithelial wound healing, regenerative hypertrophy, compensatory hypertrophy.
Epithelialization during the healing of wounds with a disturbed epithelial cover, it goes about the same, regardless of whether the organ will be regenerated further by epimorphosis or not. Epidermal wound healing in mammals in the case when the wound surface dries up with the formation of a crust, proceeds as follows (Fig. 8.25). The epithelium at the edge of the wound thickens due to an increase in cell volume and expansion of intercellular spaces. The fibrin clot acts as a substrate for the migration of the epidermis deeper into the wound. There are no mitoses in migrating epithelial cells, but they have phagocytic activity. Cells from opposite edges come into contact. Then comes the keratinization of the wound epidermis and the separation of the crust covering the wound.
Rice. 8.25. Diagram of some of the events taking place
with epithelialization of skin wounds in mammals.
A- the beginning of ingrowth of the epidermis under the necrotic tissue; B- fusion of the epidermis and separation of the scab:
1 -connective tissue, 2- epidermis, 3- scab, 4- necrotic tissue
By the time the epidermis meets the opposite edges in the cells located directly around the edge of the wound, an outbreak of mitosis is observed, which then gradually decreases. According to one version, this outbreak was caused by a decrease in the concentration of the mitosis inhibitor - keylon.
Epimorphosis represents the most obvious way of regeneration, which consists in the growth of a new organ from the amputation surface. The regeneration of the extremity of the newt and axolotl has been studied in detail. There are regressive and progressive phases of regeneration. Regressive phase begin with healing wounds, during which the following main events occur: stopping bleeding, contraction of the soft tissues of the limb stump, the formation of a fibrin clot above the wound surface and migration of the epidermis covering the amputation surface.
Then begins destruction osteocytes at the distal end of the bone and other cells. At the same time, cells participating in the inflammatory process penetrate into the destroyed soft tissues, phagocytosis and local edema are observed. Then, instead of forming a dense plexus of connective tissue fibers, as occurs during wound healing in mammals, differentiated tissues are lost in the area under the wound epidermis. Osteoclastic bone erosion is characteristic, which is a histological sign dedifferentiation. The wound epidermis, already permeated with regenerating nerve fibers, begins to thicken rapidly. The spaces between the tissues are more and more filled with mesenchymal cells. The accumulation of mesenchymal cells under the wound epidermis is the main indicator of the formation of regenerative blastema. The blastema cells look the same, but it is at this point that the main features of the regenerating limb are laid.
Then begins progressive phase, for which the processes of growth and morphogenesis are most characteristic. The length and mass of the regenerative blastema increase rapidly. The growth of the blastema occurs against the background of the formation of limb features in full swing, i.e. its morphogenesis. When the shape of the limb has already taken shape in general terms, the regenerate is still smaller than the normal limb. The larger the animal, the greater this difference in size. To complete morphogenesis, time is required, after which the regenerate reaches the size of a normal limb.
Some stages of regeneration of the forelimb in the newt after amputation at the shoulder level are shown in Fig. 8.26. The time it takes for a limb to fully regenerate varies with the size and age of the animal and the temperature at which it occurs.
Rice. 8.26. Regeneration stages of the forelimb in the newt
In young axolotl larvae, the limb can regenerate in 3 weeks, in adult newts and axolotls in 1-2 months, and in terrestrial ambistas, this takes about 1 year.
During epimorphic regeneration, an exact copy of the removed structure is not always formed. This regeneration is called atypical. There are many types of atypical regeneration. Hypomorphosis - regeneration with partial replacement of the amputated structure. For example, an adult clawed frog develops an styloid structure instead of a limb. Heteromorphosis - the appearance of another structure in place of the lost one. This can manifest itself in the form of homeotic regeneration, which consists in the appearance of a limb at the site of the antennae or an eye in arthropods, as well as in a change in the polarity of the structure. From a short fragment of a planarian, a bipolar planarian can be stably obtained (Fig. 8.27).
The formation of additional structures occurs, or excessive regeneration. After the incision of the stump with amputation of the head section of the planaria, regeneration of two or more heads occurs (Fig. 8.28). You can get more fingers during axolotl limb regeneration by rotating the end of the limb stump 180 °. Additional structures are mirror images of the original or regenerated structures next to which they are located (Bateson's Law).
Rice. 8.27. Bipolar planaria
Morphallaxis - it is regeneration by rebuilding the regenerating site. An example is the regeneration of a hydra from a ring cut from the middle of its body, or the restoration of a planarian from one tenth or twentieth of its part. In this case, there are no significant morphogenetic processes on the wound surface. The cut off piece is compressed, the cells inside it are rearranged, and a whole individual appears
reduced in size, which then grows. This method of regeneration was first described by T. Morgan in 1900. In accordance with his description, morphallaxis is carried out without mitosis. Often there is a combination of epimorphic growth at the site of amputation with reorganization by morphallaxis in the adjacent parts of the body.
Rice. 8.28. Multi-headed planarian obtained after head amputation
and making incisions on the stump
Regenerative hypertrophy refers to the internal organs. This method of regeneration consists in increasing the size of the remainder of the organ without restoring its original shape. An illustration is the regeneration of the liver of vertebrates, including mammals. With a marginal injury to the liver, the removed part of the organ is never restored. The wound surface heals. At the same time, cell multiplication (hyperplasia) increases inside the remaining part, and within two weeks after removal of 2/3 of the liver, the original mass and volume are restored, but not the shape. The internal structure of the liver is normal, the lobules have a typical size for them. Liver function also returns to normal.
Compensatory hypertrophy consists in changes in one of the organs with a violation in the other, belonging to the same organ system. An example is hypertrophy in one of the kidneys when the other is removed, or swollen lymph nodes when the spleen is removed.
The last two methods differ in the place of regeneration, but their mechanisms are the same: hyperplasia and hypertrophy.
The restoration of individual mesodermal tissues, such as muscle and skeletal tissues, is called tissue regeneration. For muscle regeneration, it is important to preserve at least small stumps at both ends, and for bone regeneration, the periosteum is necessary. Regeneration by induction occurs in certain mammalian mesodermal tissues in response to the action of specific inducers that are introduced into the damaged area. This method manages to obtain complete replacement of the defect in the bones of the skull after the introduction of bone sawdust into it.
Thus, there are many different ways or types of morphogenetic phenomena in the restoration of lost and damaged parts of the body. The differences between them are not always obvious, and a deeper understanding of these processes is required.
The study of regenerative phenomena concerns not only external manifestations. There are a number of issues of problematic and theoretical nature. These include issues of regulation and conditions in which recovery processes take place, issues of the origin of cells involved in regeneration, the ability to regenerate in various groups, animals, and the characteristics of recovery processes in mammals.
It was found that in the limb of amphibians after amputation and in the process of regeneration, real changes in electrical activity occur. When an electric current is passed through an amputated limb in adult clawed frogs, an increase in the regeneration of the forelimbs is observed. The amount of nerve tissue in the regenerates increases, from which it is concluded that the electric current stimulates the ingrowth of nerves into the edges of the extremities, which are not normally regenerating.
Attempts to stimulate limb regeneration in mammals in this way have been unsuccessful. So, under the action of an electric current or with a combination of the action of an electric current with a nerve growth factor, it was possible to obtain in a rat only an overgrowth of skeletal tissue in the form of cartilaginous and bone calluses, which did not resemble the normal elements of the limb skeleton.
Undoubtedly, the regulation of regeneration processes by nervous system. With careful denervation of the limb during amputation, epimorphic regeneration is completely suppressed and blastema never forms. Interesting experiments were carried out. If the nerve of the extremity of the newt is taken under the skin of the base of the limb, then an additional limb is formed. If it is taken to the base of the tail, the formation of an additional tail is stimulated. The abduction of the nerve to the lateral region does not cause any additional structures. These experiments led to the creation of the concept regeneration fields. .
It was found that the number of nerve fibers is decisive for the initiation of regeneration. The type of nerve does not matter. The influence of nerves on regeneration is associated with the trophic effect of nerves on the tissues of the extremities.
Data obtained in favor of humoral regulation regeneration processes. A particularly common model for studying this is the regenerating liver. After the introduction of serum or blood plasma from animals that underwent removal of the liver to normal intact animals, stimulation of the mitotic activity of liver cells was observed in the former. In contrast, when serum from healthy animals was administered to injured animals, a decrease in the number of mitoses in the damaged liver was obtained. These experiments may indicate both the presence of regeneration stimulants in the blood of injured animals and the presence of cell division inhibitors in the blood of intact animals. The explanation of the experimental results is complicated by the need to take into account the immunological effect of injections.
The most important component of humoral regulation of compensatory and regenerative hypertrophy is immunological response. Not only partial removal of an organ, but also many influences cause disturbances in the immune status of the organism, the appearance of autoantibodies and stimulation of the processes of cell proliferation.
There is great disagreement on the issue of cellular sources regeneration. Where do undifferentiated blastema cells that are morphologically similar to mesenchymal cells come from or how do they appear? There are three assumptions.
1. Hypothesis reserve cells implies that the precursors of the regenerative blastema are the so-called reserve cells, which stop at some early stage of their differentiation and do not participate in the development process until they receive a stimulus for regeneration.
2. Hypothesis temporary dedifferentiation, or modulation of cells suggests that in response to a regenerative stimulus, differentiated cells can lose signs of specialization, but then they again differentiate into the same cell type, i.e., having lost their specialization for a while, they do not lose determination.
3. Hypothesis complete dedifferentiation specialized cells to a state similar to mesenchymal cells and with possible subsequent transdifferentiation or metaplasia, i.e. transformation into cells of a different type, believes that in this case the cell loses not only specialization, but also determination.
Modern research methods do not allow to prove all three assumptions with absolute certainty. Nevertheless, it is absolutely true that chondrocytes are released from the surrounding matrix in the stumps of the axolotl's fingers and migrate into the regenerative blastema. Their further fate has not been determined. Most researchers recognize dedifferentiation and metaplasia during lens regeneration in amphibians. The theoretical significance of this problem lies in the assumption that it is possible or impossible for the cell to change its program to such an extent that it returns to a state where it is again capable of dividing and reprogramming its synthetic apparatus. For example, a chondrocyte becomes a myocyte or vice versa.
The ability to regenerate is not unambiguously dependent on organization level, although it has long been noticed that lower organized animals have a better ability to regenerate external organs. This is confirmed by amazing examples of the regeneration of hydra, planarians, annelids, arthropods, echinoderms, lower chordates, such as ascidians. Of the vertebrates, tailed amphibians have the best regenerative ability. It is known that different species of the same class can differ greatly in their ability to regenerate. In addition, when studying the ability to regenerate internal organs, it turned out that it is significantly higher in warm-blooded animals, for example, in mammals, in comparison with amphibians.
Regeneration at mammals differs in originality. For the regeneration of some external organs, special conditions are needed. The tongue, ear, for example, does not regenerate in the event of a marginal injury. If a through defect is applied through the entire thickness of the organ, the restoration is going well. In some cases, the regeneration of the nipples was observed even when they were amputated at the base. The regeneration of internal organs can be very active. A whole organ is restored from a small fragment of the ovary. The features of liver regeneration have already been mentioned above. Various mammalian tissues also regenerate well. There is an assumption that the impossibility of regeneration of extremities and other external organs in mammals is of an adaptive nature and is due to selection, since with an active lifestyle, gentle morphogenetic processes would make life difficult. The achievements of biology in the field of regeneration are successfully applied in medicine. However, there are a lot of unresolved issues in the problem of regeneration.
Regeneration - the process of secondary development of an organ or tissue caused by damage of some kind.
Regeneration occurs at all levels of matter
By the ability to regenerate there are 3 groups of tissues and organs:
1. Regenerative reaction in the form of cell neoplasms: skin epithelium, bone marrow, bone tissue, small intestine epithelium, lymphatic system.
2. Intermediate form. Cell division and intracellular regeneration take place. Liver, lungs, kidneys, adrenal glands, skeletal muscles.
3. Intracellular regeneration predominates. Cells of the central nervous system, myocardium.
Physiological regeneration- restoration of body parts worn out in the process of life. It acts throughout ontogenesis, maintains the constancy of structures, despite cell death. Intensive processes of physiological regeneration during the restoration of blood cells, epidermis, mucous membranes. Examples include bird molt, tooth growth in rodents. Physiological regeneration occurs not only in tissues with intensively dividing cells, but also where cells are dividing slightly. 25 hepatocytes out of 1000 die and the same number are restored. Physiological regeneration is a dynamic process that includes cell division and other processes. The provision of functions is the basis for the normal functioning of the body.
Physiological regeneration is the process of renewing the functioning structures of the body. Due to physiological regeneration, structural homeostasis is maintained and the organs can constantly perform their functions. From a general biological point of view, physiological regeneration, like metabolism, is a manifestation of such an important property of life as self-renewal.
Examples of physiological regeneration at the cellular and tissue levels are the renewal of the epidermis of the skin, the cornea of the eye, the epithelium of the intestinal mucosa, peripheral blood cells, etc.
Derivatives of the epidermis - hair and nails - are renewed. This is the so-called proliferative regeneration, i.e. replenishment of the number of cells due to their division.
In physiological regeneration, two phases are distinguished: destructive and restorative. It is believed that the decay products of some cells stimulate the proliferation of others. Hormones play an important role in the regulation of cellular renewal.
Reparative regeneration, its significance. Methods of reparative regeneration. Manifestation of regenerative capacity in phylogenesis. Molecular genetic, cellular and systemic mechanisms of regeneration. Features of the recovery processes in mammals.
Reparative (restorative) regeneration- restoration of damaged tissues and organs after extreme impacts. With complete regeneration, the complete original structure of the tissue is restored after its damage, its architecture remains unchanged. Distributed in organisms capable of asexual reproduction. For example, white planarian, hydra, molluscs (if you remove the head, but leave the nerve - nodal structure). Typical reparative regeneration is possible in higher organisms, incl. and a person. For example, when eliminating necrotic organ cells. In the acute stage of pneumonia, the destruction of the alveoli and bronchi occurs, then recovery occurs. Under the action of hepatotropic poisons, diffuse necrotic changes in the liver occur. After the cessation of the action of poisons, the architectonics is restored due to the division of hepatocytes - cells of the hepatic parenchyma. The original structure is restored. Homomorphosis- restoration of the structure in the form in which it existed before destruction. Incomplete reparative regeneration - the regenerated organ differs from the removed one - heteromorphosis... The original structure is not restored, and sometimes another organ develops instead of one organ. For example, an eye in cancer. When removed, in some cases, an antenna develops. In humans, the liver, when part of the hepatic lobe is removed, similarly regenerates. A scar appears and after 2 - 3 months after the operation, the mass of the liver is restored, but the restoration of the organ's shape does not occur. This is due to the removal and damage of connective tissue during surgery.
Excessive regeneration- the formation of additional structures. After the incision of the stump during amputation of the head section of the planaria, regeneration of two or more heads occurs.
In mammals, all 4 types of tissue can regenerate:
1. Connective tissue... Loose connective tissue has a high ability to regenerate. Interstitial components regenerate best of all - a scar is formed, which is replaced by tissue. Bone tissue is similar. The main elements that restore tissue are osteoblasts (poorly differentiated cambial cells of bone tissue);
2. Epithelial tissue... Possesses a pronounced regenerative reaction. Skin epithelium, cornea of the eye, mucous membranes of the mouth, lips, nose, gastrointestinal tract, bladder, salivary glands, renal parenchyma. In the presence of irritating factors, pathological processes can occur that lead to tissue proliferation, which leads to cancerous tumors.
3. Muscle tissue... It regenerates significantly less than epithelial and connective tissues. Transverse musculature - amitosis, smooth - mitosis. Regenerates due to undifferentiated satellite cells. Individual fibers and even whole muscles can grow and regenerate.
4. Nerve tissue... Poor regeneration ability. The experiment showed that cells of the peripheral and autonomic nervous systems, motor and sensory neurons in the spinal cord regenerate little. Axons regenerate well due to Schwann cells. In the brain, instead of them, there is glia, so regeneration does not occur.
methods of reparative regeneration:
· Epithelialization-healing of epithelial wounds.
· Epimorphosis- regrowth of a new organ from the amputation surface
· Morfollaxis- regeneration by restructuring the regenerating site (An example is the regeneration of a hydra from a ring cut from the middle of its body, or the restoration of a planarian from one tenth or twentieth of its part.)
· Regenerative hypertrophy- to the internal organs. This method of regeneration consists in increasing the size of the remainder of the organ without restoring its original shape. (Liver regeneration (hypeoplasia), the original function, mass and volume are restored, but not the shape)
· Compensatory hypertrophy- consists in changes in one of the organs in case of violation in the other, belonging to the same organ system. (hypertrophy in one of the kidneys when the other is removed, or swollen lymph nodes when the spleen is removed.)
Biological and medical significance of the problem of regeneration. Manifestation of regenerative capacity in humans. Regeneration of pathologically altered organs and reversibility of pathologically altered organs. Regeneration therapy.
When cut, blood rushes into the wound, the leukocytes of which start the inflammatory process. The cells of the adjacent epithelial tissue divide and form a "scab" (scar). Then the healing process begins.
At present, the problems of regeneration, especially those related to medicine, are being intensively studied. Stem cells have properties:
The stem cell is not definitively differentiated (rather, it is determined);
The stem cell is capable of unlimited division;
When dividing, some of the cells remain stem cells, while the other part undergoes the process of differentiation.
There are very few centers for the use of stem cells, in Russia there are only 2 such centers. However, stem cells are everywhere. For treatment and experiments, cord blood is taken in order to obtain stem cells.
The bones of the skull do not normally regenerate. Under the leadership of II Polezhaev, a 10x10 cm section of the dog's skull was removed. Bone sawdust was obtained from the bone by grinding, which was placed on the wound. In another experiment, bone filings from a donor and the blood of a recipient were used. A week later, sawdust resorbed, and by the end of 1 year the wound was healed.
Regeneration after radiation exposure is of great importance. Small doses stimulate, and large ones, on the contrary, inhibit this process.
If you carry out mechanical crushing of the stump or placing it in acid, regeneration occurs in 50% of cases.
Elizarov performed breaking and lengthening of bones. He created unique devices, thanks to which it was possible to expand the bones of the skeleton and correct their shape.
The problem of liver regeneration is acute. With cirrhosis of the liver, it is necessary to carry out its partial removal. Sometimes such an operation is performed several times, the liver quickly regenerates without retaining its shape, maintaining function and total mass.
Regeneration can be stimulated with anticeylon, vitamin B12, ATP, RNA.
There are types of regeneration in pathologically altered organs.
Regeneration after exposure to toxic substances.
Regeneration after exposure to harmful physical factors.
Regeneration after diseases caused by microorganisms and viruses.
Regeneration after blood supply failure.
Regeneration after hunger, hypokinesia (immobilization), atrophy.
Regeneration after damage caused in the body by organ dysfunction.
78. The concept of homeostasis. General laws of homeostasis of living systems. Genetic, cellular and systemic bases of the body's homeostatic reactions. The role of the endocrine, nervous and immune systems in providing homeostasis and adaptive changes.
The term "homeostasis" was proposed to understand the constancy of the composition of lymph, blood and tissue fluid. Homeostasis is characteristic of any system; it is a kind of generalization of many particular manifestations of the stability of the system.
Homeostasis - maintaining the constancy of the internal environment of the body in the constantly changing conditions of the external environment. Because an organism is a multilevel self-regulating object; it can be viewed from the point of view of cybernetics. Then, the body is a complex multi-level self-regulating system with many variables.
Input variables:
Cause;
Irritation.
Output variables:
Reaction;
Consequence.
The reason is a deviation from the normal reaction in the body. Feedback plays a decisive role. There is positive and negative feedback.
Negative feedback reduces the effect of the input signal on the output signal. Positive feedback increases the action of the input signal to the output effect of the action.
A living organism is an ultrastable system that searches for the most optimal stable state, which is provided by adaptations.
Adaptation- maintenance of variable indicators at the behavioral, anatomical, biochemical and other levels.
Ethology- a science that studies the behavior of animals and humans. The types of behavior of animals and humans are limited by their morphological and physiological characteristics. A person has a dependence of behavior on the type of addition. There are 3 types of addition:
endomorphic;
ectomorphic;
mesomorphic.
Animals can improve their movements through information, in addition, they have the ability to regulate them. Animals must distinguish objects of the external environment, receive information with the help of their senses. The information received is processed by the nervous and endocrine systems. Many types of behavior can cause hormonal changes.
Morphological and physiological characteristics are subject to natural selection, behavior, in turn, depends on these characteristics, and therefore depends on natural selection. Behavior is inherited, increases adaptability, increases life expectancy, and the number of offspring. Various behavioral reactions allow the use of favorable environmental conditions, protect the body from adverse conditions. For example, in bees, keeping the hive clean. At least 2 genes are responsible for hygienic behavior. Maintaining cleanliness protects bees from disease. The lizard's behavior, dropping its tail, if necessary, is also an adaptive response. Other types of behavioral reactions are observed when protecting from predators, when searching for food, a partner, protecting offspring, and in many other cases. Some insects secrete special chemicals called pheromones to attract offspring. During the mating season, frogs croak and their "song" is species-specific.
Behavioral traits have not only adaptive properties, but can also be inherited, which determines natural selection. Not all behaviors are derived from transmission with genes, they can be acquired - acquired. It is impossible to draw a sharp border between the one and the other, because genes and the environment closely interact with each other, therefore, it is impossible to separate genetic and acquired properties.
The following examples of genetic properties can be cited. Chorea of Huntington is a hereditary disease, "dance", affects the central nervous system, patients also have impaired spatial orientation. Another example, downs are benevolent, affectionate, imitate the actions of healthy people.
So, important behavioral properties:
Behavior is subject to natural selection;
Behavioral traits arise from the anatomy, morphology, and physiology of the animal are inseparable about them;
Behaviors are usually adaptive and can often be transmitted either genetically or through learning;
Many species have specific behaviors.
If the body has not been able to adapt at the behavioral level, it does so at the biochemical level. Biochemical adaptation is very complex, most typical for plants, because it is easier for an animal to migrate.
The adaptation process takes place in time:
Evolutionary adaptation;
Acclimatization;
Immediate adaptation.
Evolutionary adaptation- a long-term process, the acquisition of new genetic information, the genotype changes, therefore, the phenotype also changes. This adaptation takes many generations to complete.
Acclimatization- adaptations that occur during life in natural conditions.
Acclimation- adaptations taking place in artificial conditions.
Occurs over several hours - years (winter - summer). Change of time zones, translation of time.
Immediate adaptation accompanied by an almost instantaneous adaptive response (psychogenic effect, transition from heat to cold). Short-term reaction.
Any adaptation occurs as a result of the interaction of genetic factors and environmental factors.
Genetic aspect homeostasis is considered from 3 positions:
Genotype homeostasis;
Homeostasis of the organism as a whole. Control over the unity of the genotype of the whole organism. Maintaining homeostasis is carried out with the death of modified cells.
Population homeostasis. The law of genetic stability in a population.
Various systems are involved in maintaining homeostasis.
Nervous alarm- the main tool for transmitting and evaluating signals from the internal and external environment.
Hormones take part in the regulation of homeostasis. Regulate metabolism, water, proteins, lipids, carbohydrates, energy, electrolytes. They control the work of all organs, including kidneys, liver, central nervous system.
The immune system protects the constancy of the internal environment of the body from factors of 2 groups:
Microorganisms and exogenous factors with signs of foreign genetic information;
Somatic mutations. Changes in one or two genes are enough for the immune system to work.
79. Problems of organ and tissue transplantation. Auto-, allo- and xenotransplantation, transplantation of vital organs. Immunity. Tissue incompatibility and ways to overcome it. Artificial organs.
Due to the rapid development transplantology the question of transplant immunity arose sharply.
Transplantology- biomedical science, which studies the issues of procurement, conservation and transplantation of organs and tissues.
Transplant immunity- a kind of reaction of the body to transplantation, manifested in the rejection of transplanted organs and tissues.
Classification of terms (Vienna, 1967).
Graft- transplanted tissue or organ.
Recipient- the one to whom the organ or tissue is transplanted.
Donor- the one from whom the transplant is taken.
Autotransplantation- transplantation of tissues and organs within the same organism (in this case, they speak of an autograft)
Isotransplantation(isograft) - transplantation of tissues and organs between organisms that are genetically identical.
Allotransplantation(allograft) - transplantation of tissues and organs between organisms of the same biological species.
Xenotransplantation(xenograft) - transplantation of tissues and organs between organisms of different biological species.
Explantation(explant) - transplantation of non-biological material.
Combined transplant(combined graft).
There are two acute problems: the preservation of organs and tissues with their unchanged properties. Another problem is overcoming transplant immunity.
Different methods of conservation.
1) Cooling (short-term).
2) Freezing.
3) Lyophilization.
Freezing can rupture tissue, resulting in tissue death. But sperm are able to live. The state of suspended animation in some animals. The blood is replaced with cryoprotectants, after defrosting, a reverse replacement is performed. Lyophilization method - freezing by drying in air. Storing frozen people. There are tissue banks, organ banks on a scientific basis.
Overcoming tissue incompatibility is the work of surgeons, immunologists, physiologists and other specialists. A whole medical area - immunosuppressive therapy- aims to solve this problem. Chemical, physical and biological factors are used to influence the recipient's body.
Physical methods- radioactive radiation, X-rays.
Chemical methods- the introduction of drugs that reduce immunity. They strongly affect the vital organs.
Biological methods- the introduction of antitoxic sera, antibiotics. The principle of action is the neutralization of transplant antibodies. Most promising method.
Currently, almost everything is transplanted: both organs and tissues.
The history of transplantation in Russia.
1933 - Yu.Voronov - the world's first kidney transplant.
1937 - Demikhov - the first heart transplant for a dog in the USSR.
1946 - Demikhov - transplanted a heart and lungs to a dog.
1948 - Demikhov, Shvekovsky - liver transplant for a dog.
1954 - Demikhov transplanted a second head to a dog.
1965 - Petrovsky - the first successful kidney transplant.
1986 - Shumakov - the first human heart transplant in the USSR (1967 - Christian Bernard - South Africa - a successful human heart transplant).
1990 - Eramishantsev - the first human liver transplant in the USSR.
There is a kidney transplant center in Voronezh. At the Charite clinic in Germany, 60-100 liver transplants are performed annually.
In 2005, a successful liver transplant operation was performed in England from one donor - a child and an adult.
Despite the merits, transplantation is limited by law, and in addition, many organs are "scarce".
80.Biological rhythms. Chronobiology and chronomedicine.
The science that studies biorhythms - biorhythmology.
Biological rhythm- fluctuation of the rhythm or speed of any biological process, which occurs approximately at regular intervals. Biological rhythms are inherent in all living organisms.
From the point of view of the interaction of the organism and the environment, there are:
- adaptive rhythms (ecological). Oscillations with periods close to the main geophysical rhythms. (lunar, annual, seasonal, tidal rhythms).
- physiological (working) rhythms.
Oscillations reflecting the activity of the working systems of the body's organs.
Classification of biorhythms.
1. High frequency rhythms.
Oscillations are performed with a period from fractions of a second to 30 minutes. ECG rhythms, contractions of the heart, respiration, gastrointestinal motility.
Medium frequency rhythms.
From 30 minutes to 28 hours.
· ultradian-up to 20 hours. (alternation of REM and slow sleep. Oral behavior.)
· circadian 20-28 hours. These are modified diurnal rhythms. They are congenital, endogenous, due to the properties of the organism and its genotype. Found in all organisms. (blood pressure, pulse, change in body temperature)
Mesorhythms.
· Infrared -28 hours-6 days. (beard growth, heart contractions)
Circaseptal - about 7 days (mosquitoes lay eggs after 7 days, pineal gland hormone activity, mortality from non-infectious diseases, rejection and engraftment of the graft.)
Macro rhythms
20 days - year
Megarithms.
Periods of tens of years.
Of all the variety of rhythmic processes, the main focus is on the diurnal and seasonal rhythms. Daily and seasonal rhythm occurs at all levels of biological reactions. Rhythms serve 2 purposes: adaptation of organisms to expected environmental conditions, compilation of a unique time system, integration of all rhythms together.
The concept of a cycle implies the periodicity of the process. The time between the same states of neighboring rhythms - period T... Cycles per unit of time - frequency... The value that corresponds to the average value of the useful signal - meser. The largest deviation from the meser is amplitude... The moment in time when a specific value is recorded - phase. The moment of the greatest rise - acrophase, the moment of the least rise - bathyphase.
Diseases associated with disturbances in biological rhythms - desynchronosis.
They can be explicit and hidden.
Explicit desynchronosis differs in the presence of a breakdown, rapid fatigue, increased heart rate, blood pressure, breathing.
Latent desynchronosis leads to discomfort, sleep and appetite disturbances. This is a pre-morbid condition.
total desynchronosis... In this case, general changes occur in all organ systems.
partial desynchronosis, in this case, there are failures of individual organs and their functions.
Chronic desynchronosis occurs due to frequent deviations from the usual mode of life.
Spicy- arises from a strong, gross violation of the regime of work and rest, sleep, nutrition. The sharpest is observed in children and the elderly.
Rhythm initially arises as a result of periodic exposure to the environment, then it is genetically fixed.
From biorhythmology stood out:
Chronobiology;
Chronopathology;
Chronodiagnostics;
Chronotherapy;
Chronopharmacology (taking drugs at a specific time);
Chronohygiene (compliance with the work rest regimen).
Chronobiology- a section of biology that studies biological rhythms, the course of various biological processes (mainly cyclical) in time.
Chronomedicine is the use of the laws of biorhythms to improve the prevention, diagnosis and treatment of human diseases.
81.Biological evolution. Modern theories of evolution.
Evolution principles (according to Lamarck)
Biological evolution is based on the processes of self-reproduction of macromolecules and organisms.
Biological evolution- irreversible and directed historical development of living nature, it is accompanied by:
Changes in the genetic makeup of the population;
Formation of adaptations;
Formation and extinction of species;
The transformation of ecosystems and the biosphere as a whole.
LECTURE No. 14
- Regenerative response levels.
- Physiological repair.
- Reparative regeneration.
- Manifestation of regeneration in ontogeny and phylogeny.
The most important problem of medicine is the restoration of damaged tissues and organs and their return to their functions. The problem is medical, but its basis is biological.
Regeneration - the process of secondary development of an organ or tissue caused by damage of some kind.
Primary development is ontogenesis.
Secondary development - development associated not with natural reproduction, but with external influences, but the body. External influence involves definitive organs and tissues in the development process. Darwin emphasized that sexual reproduction, asexual reproduction and regeneration are manifestations of one and the same property of the organism.
Regeneration occurs at all levels of matter.
In the process of life, the structure of DNA changes - molecular regeneration.
Regeneration can take place inside organelles - intraorganoid regeneration. The cristae of mitochondria, cisterns of the Golgi complex, parts of the ER, etc. are restored. For example, the hepatocyte of a person who abuses alcohol.
Regeneration of whole organelles is possible - organoid... The number of mitochondria, lysosomes and other organelles is restored - hyperplasia.
Together, these 3 levels of regeneration make up intracellular regeneration.
Cellular regeneration - an increase in the number of cells.
By the ability to regenerate there are 3 groups of tissues and organs:
1. Regenerative reaction in the form of cell neoplasms: skin epithelium, bone marrow, bone tissue, small intestine epithelium, lymphatic system.
2. Intermediate form. Cell division and intracellular regeneration take place. Liver, lungs, kidneys, adrenal glands, skeletal muscles.
3. Intracellular regeneration predominates. Cells of the central nervous system, myocardium.
Regeneration is inherent in all organisms. With the loss or absence of the ability for asexual reproduction, the ability for somatic regeneration is lost (the body does not form from a part of the body, but the regenerative function of certain parts of the body is preserved).
Regeneration can be physiological and reparative. In turn, reparative regeneration is of several types:
Indemnifying;
Post-traumatic;
Recovery;
Pathological.
According to the degree of recovery, reparative repair can be typical (complete) - homomorphosis, morpholaxis and atypical - incomplete, heteromorphosis.
Physiological regeneration- restoration of body parts worn out in the process of life. It acts throughout ontogenesis, maintains the constancy of structures, despite cell death. Intensive processes of physiological regeneration during the restoration of blood cells, epidermis, mucous membranes. Examples include bird molt, tooth growth in rodents. Physiological regeneration occurs not only in tissues with intensively dividing cells, but also where cells are dividing slightly. 25 hepatocytes out of 1000 die and the same number are restored. Physiological regeneration is a dynamic process that includes cell division and other processes. The provision of functions is the basis for the normal functioning of the body.
Reparative regeneration- restoration of damaged tissues and organs after extreme impacts. With complete regeneration, the complete original structure of the tissue is restored after its damage, its architecture remains unchanged. Distributed in organisms capable of asexual reproduction. For example, white planarian, hydra, molluscs (if you remove the head, but leave the nerve - nodal structure). Typical reparative regeneration is possible in higher organisms, incl. and a person. For example, when eliminating necrotic organ cells. In the acute stage of pneumonia, the destruction of the alveoli and bronchi occurs, then recovery occurs. Under the action of hepatotropic poisons, diffuse necrotic changes in the liver occur. After the cessation of the action of poisons, the architectonics is restored due to the division of hepatocytes - cells of the hepatic parenchyma. The original structure is restored. Homomorphosis is the restoration of a structure in the form in which it existed before destruction. Incomplete reparative regeneration - the regenerated organ differs from the remote one - heteromorphosis. The original structure is not restored, and sometimes another organ develops instead of one organ. For example, an eye in cancer. When removed, in some cases, an antenna develops. In humans, the liver, when part of the hepatic lobe is removed, similarly regenerates. A scar appears and after 2 - 3 months after the operation, the mass of the liver is restored, but the restoration of the organ's shape does not occur. This is due to the removal and damage of connective tissue during surgery.
In mammals, all 4 types of tissue can regenerate.
1. Connective tissue... Loose connective tissue has a high ability to regenerate. Interstitial components regenerate best of all - a scar is formed, which is replaced by tissue. Bone tissue is similar. The main elements that restore tissue are osteoblasts (poorly differentiated cambial cells of bone tissue);
2. Epithelial tissue... Possesses a pronounced regenerative reaction. Skin epithelium, cornea of the eye, mucous membranes of the mouth, lips, nose, gastrointestinal tract, bladder, salivary glands, renal parenchyma. In the presence of irritating factors, pathological processes can occur that lead to tissue proliferation, which leads to cancerous tumors.
3. Muscle tissue... It regenerates significantly less than epithelial and connective tissues. Transverse musculature - amitosis, smooth - mitosis. Regenerates due to undifferentiated satellite cells. Individual fibers and even whole muscles can grow and regenerate.
4. Nerve tissue... Poor regeneration ability. The experiment showed that cells of the peripheral and autonomic nervous systems, motor and sensory neurons in the spinal cord regenerate little. Axons regenerate well due to Schwann cells. In the brain, instead of them, there is glia, so regeneration does not occur.
With the regeneration of the myocardium and the central nervous system, a scar is first formed, and then regeneration occurs due to an increase in the size of cells, intracellular regeneration also takes place. Myocardial cells do not divide by mitosis. The difference is due to development in the embryonic period. In adult organisms, EPR functions very powerfully and this inhibits cell division.
Limb regeneration process in newt / salamander.
After amputation, limb regeneration occurs in a strictly orderly manner, always in the same way. The recovering end is rounded, then takes on a conical shape, grows in length, becomes like a flipper. Then the fingers are laid. By week 8, limb regeneration is complete.
At the cellular level, several phases of limb regeneration are distinguished:
1) the phase of wound healing;
2) dismantling process;
3) the phase of "conical blastema";
4) phase of redifferentiation.
Wound healing phase... During this period, cells overgrow the wound on the stump, an apical "cap" appears (if the contact is broken, there will be no regeneration).
Dismantling process... After healing, tissue resorption occurs in the tissues adjacent to the stump. Muscle fibers lose their order, become "disheveled". In the bone tissue, the periosteum is lost, giant phagocytic cells with at least 3 nuclei appear. These cells take up the matrix and make room for new bone and cartilage to grow, removing waste material. The end of the stump becomes edematous and protrudes. The cult accumulates dedifferentiated cells of the same type, similar to embryonic cells. After a while, division of dedifferentiated cells begins.
Nerves grow into the growing stump, and stage of "conical blastema". The limb has the shape of a flipper, cell mass increases, blood flow is restored. A "regenerative kidney" appears.
Redifferentiation phase... The limb lengthens, redifferentiation begins, and the regeneration process comes to an end. If the limb is denervated, regeneration will not take place. nerve tissue performs endocrine, conductive functions. In addition, the nervous tissue secretes a protein hormone, under the control of which regeneration is carried out.
The regeneration process in humans.
When cut, blood rushes into the wound, the leukocytes of which start the inflammatory process. The cells of the adjacent epithelial tissue divide and form a "scab" (scar). Then the healing process begins.
At present, the problems of regeneration, especially those related to medicine, are being intensively studied. Stem cells have properties:
The stem cell is not definitively differentiated (rather, it is determined);
The stem cell is capable of unlimited division;
When dividing, some of the cells remain stem cells, while the other part undergoes the process of differentiation.
There are very few centers for the use of stem cells, in Russia there are only 2 such centers. However, stem cells are everywhere. For treatment and experiments, cord blood is taken in order to obtain stem cells.
The bones of the skull do not normally regenerate. Under the leadership of II Polezhaev, a 10x10 cm section of the dog's skull was removed. Bone sawdust was obtained from the bone by grinding, which was placed on the wound. In another experiment, bone filings from a donor and the blood of a recipient were used. A week later, sawdust resorbed, and by the end of 1 year the wound was healed.
Regeneration after radiation exposure is of great importance. Small doses stimulate, and large ones, on the contrary, inhibit this process.
If you carry out mechanical crushing of the stump or placing it in acid, regeneration occurs in 50% of cases.
Elizarov performed breaking and lengthening of bones. He created unique devices, thanks to which it was possible to expand the bones of the skeleton and correct their shape.
The problem of liver regeneration is acute. With cirrhosis of the liver, it is necessary to carry out its partial removal. Sometimes such an operation is performed several times, the liver quickly regenerates without retaining its shape, maintaining function and total mass.
Regeneration can be stimulated with anticeylon, vitamin B12, ATP, RNA.
Allocate types of regeneration in pathologically altered organs.
1. Regeneration after exposure to toxic substances.
2. Regeneration after exposure to harmful physical factors.
3. Regeneration after diseases caused by microorganisms and viruses.
4. Regeneration after blood supply failure.
5. Regeneration after hunger, hypokinesia (immobilization), atrophy.
6. Regeneration after damage caused in the body by organ dysfunction.
