CELL — the elementary live system consisting of two main parts — the nuclear device and cytoplasm and having ability to exchange with the environment; is the cornerstone of a structure, development and life activities of animal and vegetable organisms.
To. exist as independent cells organisms (see. Bacteria , Protozoa ) or are a part of fabrics of metaphytes, representing the elements subordinated to a complete organism; are intermediate To. colonial protozoa. Emergence of multicellularity led to specialization separate To., to division of functions between them, to formation of different types K. In the course of a morfofunktsionalny differentiation To. in fabrics of metaphytes there were elementary structures substantially deviating from typical To. Such deviations can go as towards complication, napr, large multinuclear complexes (simplasta, sincytia, plasmodiums), and towards simplification of the organization of a structure, napr, the mature erythrocytes of mammals deprived of kernels. Depending on an arrangement and development of the nuclear device allocate two types K.: prokariota, i.e. To., not having morphologically isolated kernel, and eukaryotes — To., which nuclear contents are isolated from cytoplasm (see. Cytoplasm , Kernel of a cell ). Bacteria, blue-green algae (blue-green seaweed) and actinomycetes belong to prokariota (see. Prokariotny organisms ), and to eukaryotes — seaweed, mushrooms, cells of the higher plants and animals.
- 1 History
- 2 Cytomorphology
- 3 Cytophysiology
- 4 The cytopathology
Opening To. it is connected with a name of the English scientist Guk (R. Hooke, 1665) who on cuts of a stopper and stalks of various plants under a microscope saw the empty cells like bee cells called by it a time, or cells. Zooblasts (the elementary organisms, erythrocytes, spermiya) were described for the first time by A. Levenguk (1695). At the same time representation about To. as about a structural element, the general both for animals, and for vegetable organisms, began to form only in 19 century in connection with improvement of a microscope and accumulation of number of observations. It was shown that the kernel is an obligatory part of animals (Ya. Purkinye, 1825) and vegetable [R. Brown, 1831] cells. In 1838 — 1839 T. Shvann on the basis of M. Shleyden's ideas of development of a cell (a hypothesis of a cytoblastoma) put forward the general theory of a cellular texture and development of animals and plants, having proved thereby unity of an origin of the organic world (see. Cellular theory ). Synthesis of these observations over reproduction To. by division allowed R. Virkhov (1855) to formulate the principle «each cell from a cell» («omnis cellula e cellula»). Use of this situation for an explanation of a pathogeny of a number of the major diseases of the person exerted huge impact on development of the theory of medicine (see. Cellular pathology ).
During the same period mitotic and meiotic division was open To., what played afterwards a crucial role in creation of the chromosomal theory heredities (see).
Invention of a supermicroscope, creation of essentially new methods of microscopic examination (polarizing, phase and contrast, fluorescent, etc.), progress molecular biology (see) approved representations about To. as to elaborate, complete live system, defined the present stage of development of science about To. — cytology (see). Versatility of a problem of a research K., specifics and a variety of methods of a research caused formation in cytology of six directions.
1. Cytomorphology, studying features of the structural organization of a cell; as the main methods of a research serve various ways of microscopy as fixed — svetooptichesky, electronic, polarizing, and live To. — the darkfield condenser, phase and contrast and luminescent microscopy (see. Microscopic methods of a research ).
2. Cytophysiology, the studying cell activity as uniform live system and its separate intracellular structures, and also relationship between them. For the solution of these tasks use various experimental methods in combination with methods cultures of cells and fabrics (see), microcinematographies (see) and micrurgy (see).
3. Cytochemistry (see), investigating the molecular organization K. and its separate components, and also the chemical changes connected with metabolic processes and functions K. Cytochemical researches are conducted by methods of visual and electronic and microscopic cytochemistry, cytophotometry (see), ultraviolet and interferential microscopy, autoradiography (see) and fractional centrifuging (see) with the subsequent chemical analysis of various fractions.
4. Cytogenetics (see), studying the phenomena of heredity and variability at the level of a cell.
5. Cytoecology (see) studies reactions To. to influences of environmental factors and mechanisms of adaptation to them.
6. Cytopathology (see), solving the problems connected with studying patol, processes in separate To. and metaphyte in general.
Due to the division of functions between To. and their specialization in the course of evolution of metaphytes created different types K. (epithelial, connective tissue, muscular, nervous, etc.). Form and sizes K. vary (fig. 1 and tsvetn. fig. 1 — 8) — from 4 — 10 microns (small lymphocytes of the person)' to several centimeters (an ovum of birds); extent of shoots nervous To. reaches 1 — 1,5 m. A feedforward between the size of an organism and the sizes K. does not exist. But at the same time form and sizes K. are one of characteristic species characters of an organism. E.g., To. than insects and amphibians having a tail is much larger, than To. reptiles, birds or mammals. To. is larger than gymnospermous plants, than To. Angiospermae, and To. is larger than monocotyledonous plants, than To. dicotyledonous. Special position is held polyploid To., which are always characterized by the big sizes. The form K is so various.: meet spherical, spindle-shaped, star-shaped To. etc.
Everyone To. (at eukaryotes) consists of the kernel and cytoplasm separated from each other and from the environment by covers. Cytoplasm contains a number of components: cytoplasmic reticulum, ribosomes, lamellar complex (Golgi's complex), mitochondrions, lysosomes and different inclusions; the cellular kernel is formed by a nuclear envelope, a karyoplasm and one or several kernels (fig. 2).
Cytoplasm represents the complex heterogeneous colloid system formed by proteins, nucleinic to-tami, lipids, carbohydrates, inorganic compounds, etc. Unlike usual colloid systems, cytoplasm (see) it is characterized by existence of the specialized structures performing specific functions. In cytoplasm K. there is a protein synthesis, lipids, carbohydrates, vitamins, processes of breath and a metabolism are carried out.
Plasma membrane (a cellular cover, a plasmolemma) forms a surface To. Through it the metabolism between is carried out To. and the environment, and also interaction between next To. (aggregation, contacts, etc.). Having selective permeability for some substances, it provides constancy of internal environment To. The cellular cover is formed by proteins, lipids (hl. obr. phospholipids) and polysaccharides. Structurally it represents three-layered education by thickness apprx. 6 — 10 nanometers, the outside and inner layer to-rogo consists of proteins, and intermediate — of lipids (tsvetn. fig. 18). At some To. the outer surface of a plasmolemma is covered with the nadmembranny layer (thickness of 0,1 — 0,5 nanometers) having an appearance of «cellular pile» (glycocalyx). This layer is formed by polysaccharides, mucopolysaccharides and glycoproteins. The glycocalyx plays an essential role at contact interactions of cells. Connect antigenic properties of a surface of cells, i.e. ability of recognition with it by cells of each other by the principle «or others», and also ability of cells to adsorb on themselves a number of substances, napr, digestive enzymes, etc. Under a plasmolemma the submembrane layer — the layer of a hyaloplasma rich with microtubules and microfibrils lies. It provides different types of the movement of a cellular surface and cells.
On the free, contacting and basal surfaces epithelial To. the special structures providing its exchange, protective and contact functions form.
Free surface such To. it is covered small (to dia. 50 — 100 nanometers, up to 2 — 3 microns long) outgrowths — microvillis which in several tens of times increase its «exchange» surface. Densely adjoining to each other (with intervals apprx. 20 nanometers), microvillis form a brush border (an epithelium of intestines, proximal departments of tubules of a kidney etc.). These structures contain a large amount of enzymes (an alkaline phosphatase, invertase, a miltaza, etc.) which promote active absorption of substances in blood.
Bonds between adjacent To. are carried out due to formation on their surface of different types of contacts: by formation of the folds coming each other (interdigitation), merges of periblasts of plasma membranes (the closing zone, dense contacts, Zonula occludens) and by means of intermediate contacts (Zonula adhaerens). One of common forms of contacts are desmosomes (see), the representing two sites of a plasmolemma symmetrically turned to each other, the divided narrow crack (20 — 25 nanometers). Each half of a desmosome under a plasmolemma has a layer of electronic and dense substance — a plate of an attachment, in a cut tonofibrils terminate. V K. invertebrates and in vegetable To. periblasts of plasma membranes form the true bridges crossing an intercellular crack (septirovanny desmosomes, plazmodesma).
A basal part of a plasmatic cover at a row K. (gyrose tubules of nephron, vascular textures of a brain, etc.) forms the numerous folds pressing in cytoplasm (a basal labyrinth, basal striation). Some proteins of a plasmolemma carry out a structural role, others are enzymes (the nucleotidase activated by ions of magnesium ATP-ase, an alkaline phosphatase, acid phosphomonoesterase RNK-aza, etc.) and provide active transport of molecules and ions through a plasmolemma.
The special role is attributed to enzyme adenylatecyclase. Believe that it at the same time matters the receptor site of a surface To. and the catalyst of intracellular transformation of ATP into cyclic AMF (see. Adenozinfosforny acids ). The last is a universal stimulator of the cellular enzymes participating in biochemical reactions To. The important part in regulation of cellular reactions by means of hormones of closed glands and mediators of a nervous system is assigned to this system. Lipids participate in transport through a plasmolemma of fat-soluble substances and electron transfer.
Hyaloplasma (the main substance of cytoplasm, a matrix) is internal environment To., in a cut - processes of exchange are carried out and cellular is supported homeostasis (see). The system of intracellular membranes (e.g., a cytoplasmic reticulum) divides cytoplasm into separate compartments (cameras, tanks) that creates a possibility of a simultaneous course of various metabolic processes in different sites of cytoplasm.
In to a hyaloplasma (see) various intracellular structures are located. The hyaloplasma has an appearance of homogenous vitreous matter. Being a colloid system, it has ability to change physical. - a chemical state (so-called transitions <>gel-sol), and its different sites can be either in liquid, or in a dense state with all transitions between them. Water, proteins, lipids, nucleinic to - you, intermediate products of their exchange, and also enzymes and inorganic matters are a part of a hyaloplasma (see. Intracellular liquid ).
In a hyaloplasma 3 groups of various intracellular structures are located: organoids, metaplasmatic educations and inclusions (paraplasmatic educations, deytoplazma). To constant structures of a hyaloplasma in animal To. carry mitochondrions, a cytoplasmic reticulum (reticulum), ribosomes, Golgi's complex, lysosomes, the cellular center, cytoplasmatic microtubules and microfibrils, and also microbodies, or peroxisomas. To the same group of structures in vegetable To. carry plastids and spherosomes, and at prokariot — mesosom. At protozoa (see), except all-cellular organoids, there are organellas performing functions of special microscopic bodies: pellicle (cover cover), throat (swallowing food), digestive vacuole (digestion of food particles), secretory vacuole (release of liquid, regulation of osmotic pressure), trikhotsist (protective device), etc.
Mitochondrions (see) in a light microscope have an appearance of small granules or sticks which sizes fluctuate within 0,2 — 2,0 microns. A basis of the ultrastructural organization of this organoid (fig. 3) are three-layered lipoproteidny membranes. Mitochondrions are limited to the cover consisting of outside and internal membranes. Folds of last (crista) press in the homogeneous matrix filling the internal camera of a mitochondrion (tsvetn. fig. 17). Due to the different biogenesis mitochondrial membranes have the different ultrastructural organization, unequal chemical structure and perform different functions. The outer membrane which arose from a plasmolemma of a host cell (a hypothesis of an endosymbiotic origin) is formed by globular proteinaceous molecules — enzymes of synthesis fat to - t, phospholipids and, apparently, a tricarboxylic cycle. The inner membrane which arose from membranes of a hypothetical cell symbiont includes the proteinaceous molecules having the forms of balls with a pedicle and the basis, contains a complete chain of electron transfer and system of interface of a cathode rays to synthesis of ATP. Mitochondrions — self-replicating structures, with own DNA and ribosomal beloksinteziruyushchy system. If control of a reproduction of an outer membrane is exercised by a cellular kernel, then self-updating of an inner membrane is regulated by mitochondrial DNA. Mitochondrions, carrying out processes of oxidation and accumulation of energy, serve as «the power station» To.
Endoplasmic reticulum (see), or the cytoplasmic reticulum, represents system of the intracellular tubules, vacuoles and tanks limited to cytoplasmic membranes (tsvetn fig. 14). Thanks to such division of internal space the possibility of simultaneous implementation of various processes in different zones K is reached. In different To. thickness of membranes varies from 4 to 7,5 nanometers, and the sizes of intra cisternal cavities — from 70 nanometers (tubules) to 500 nanometers (tank). Approximately throughout two thirds of this system of a membrane are connected with ribosomes (a granular cytoplasmic reticulum, alpha cytomembranes, an ergastoplazma), and one third of membrane system is not connected with ribosomes (an agranular cytoplasmic reticulum, beta cytomembranes). There are data on communication of a cytoplasmic reticulum with a plasmolemma, perinuclear space of a nuclear envelope, and also with Golgi's complex. Carry to system of a cytoplasmic reticulum also so-called annulate plates. They represent groups (pack) of the flattened tanks (diameter of 20 — 40 nanometers) limited to membranes which are penetrated by openings (time) with reinforced borders (ringlets). Annulate plates usually prilezhat to a nuclear envelope are also most developed in growing and proliferating To.
Ribosomes (see), or Peleyd's granules, the RNP-granule — dense spherical particles (to dia. 15 — 30 nanometers), each of which consists of big and small subunits. They contain almost equal amounts of protein and RNA. In addition to the ribosomes attached to membranes in cytoplasm free ribosomes and systems of ribosomes (polysom or polyribosomes) meet. Ribosomes are the place of synthesis of cellular proteins. This function is most actively carried out by the ribosomes connected with membranes of a cytoplasmic reticulum. During synthesis of protein they combine in polysom.
Golgi's complex (see. Golgi complex ) in a light microscope has an appearance of the complex setevidny structures (a local form) located about a kernel or the cellular center or (the multiple organization) it is formed by separate spherical, crescent or rhabdoid little bodies (dictyosomes, or Golgi's little bodies). The ultrastructure of this organoid is formed by three components: system of the flattened tanks limited to pair smooth gamma cytomembranes, small vesicles and large vacuoles (fig. 4). Golgi's complex — organoid, in Krom various paraplasmatic educations collect (granules of a secret, a yolk, lipids, acrosomes spermiyev, hemicellulose of a cell wall, etc.), and also polysaccharides and glycoproteins are synthesized. As an equivalent of this organoid at prokariot serve probably mesosom, with to-rymi connect formation of material of a cell wall at bacteria.
Lysosomes (see) represent the small little bodies limited to a single-layer membrane. Carry morphologically various types of structures to them: primary lysosomes (fig. 5), secondary lysosomes and residual little bodies. Primary lysosomes — the granules limited to an elementary membrane and containing acid hydrolases. Secondary lysosomes are formed at merge of primary lysosomes to pinotsitozny bubbles and phagosomas (phagolysosomes, digestive vacuoles) or to the destroyed dying-off structures To. — cytolysosomes (autofagiruyushchy vacuoles). Residual little bodies, or telolizosoma — the remains of digestive or autofagiruyushchy vacuoles after end of processes of digestion in them and an autolysis. Processes of intracellular digestion and defense reactions are connected with lysosomes in which acid hydrolases collect. The origin of lysosomes is connected with rich with enzymes with hydrolases with specialized area of an agranular cytoplasmic reticulum, edges lies between a cellular kernel and the deepest tanks of a complex of Golgi. Novikov (A. V. of Novykoff) and Novikov (R. M. of Novykoff) allocate this area (1978) under the name GERL (an abbreviation of words: Golgi, Endoplasmic reticulum, lysosomes).
Cellular center (fig. 6) consists of chromophilic little bodies — the centrioles surrounded with the dense site of cytoplasm — a centrosphere (microcentrum). Centrioles usually lie in couples (diplosome), being located at right angle to each other. Centrioles (tsvetn. fig. 15,16) have the form of the cylinder, a peripheral part to-rogo is formed by 9 groups (on 1 — 3 in everyone) microtubules (to dia. 15 — 20 nanometers). Peritsentriolyarny satellites are connected with active affiliated centrioles (to dia. apprx. 70 nanometers). Similarity of the ultrastructural organization of centrioles to basal little bodies of cilia and flagellums, and also participation of the cellular center in creation of the mitotic device allows to assume participation of this organoid in locomotory functions K.
Cytoplasmatic microtubules are also a component of cytoplasm. They are formed by several (7 — 15) protofibrils, each of which consists of globular proteinaceous (tubulina) subunits (on 4 nanometers). Usually microtubules go rectilinearly and between them often observe bridges. Assume * that these educations play a role of a skeleton To., participate in various forms of motion To. (the movements of cilia, flagellums), and also in intracellular transport of some substances.
Systems of the microfibrils penetrating cytoplasm diversely are close to microtubules. It is suggested about a genetic linkage between them and about development of the first by polymerization of the second. However different sensitivity to colchicine (higher at microtubules) and to cytochalasin B (is higher at microfibrils) allows to think that microfibrils represent independent system. They are considered as basic or sokratitelny elements K. (movement K. in culture, lengthening of a shoot nervous To. at regeneration, etc.).
Microbodies (peroxisoma) and related educations by it are important (multivesicular little bodies, cytosom, etc.). Many authors carry them to organoids K. These specific cytoplasmatic educations are limited to an unary membrane and or contain more dense core (nucleoid) in a fine-grained matrix, or are deprived its (anukleoid-ny). The core of one microbodies has the crystal organization (crystalloid microbodies), and at others it has no correct structure (not crystalloid microbodies). Existence of a catalase and some oxidizing enzymes is characteristic of all microbodies (urate oxidase, an oxidase - D - amino acids, etc.). Assume that microbodies are the primitive domitokhondrialny structures splitting hydrogen peroxide and providing not mitochondrial oxidation of nicotinamide adenine dinucleotide.
Kernel — the most important structure of cells eukaryotes, in a cut is concentrated ground mass deoxyribonucleic to - you are (DNA), being the carrier of genetic information. The majority To. have one kernel though meet two-and multi-core K. Yadro in To. it is always surrounded with cytoplasm, about a cut is in close interrelation. During mitotic division the kernel is reconstructed, but is always returned to a reference state upon termination of a mitosis. The sizes of a kernel are in certain dependence on type K. V K. patholologically the changed fabrics and tumors disturbance in the ratio of the size of a kernel and K.
Yadro is observed consists of 3 main components: a nuclear envelope, a karyoplasm (nucleohyaloplasm) and one or several kernels (see. Kernel of a cell ).
Nuclear envelope it is formed by outside and internal elementary lipoproteidny membranes, between to-rymi the perinuclear space which is reported with tubules of a cytoplasmic reticulum is located. As well as membranes of the last, an outer nuclear membrane it is connected with ribosomes. To an inner membrane closely prilezhit peripheral chromatin of a karyoplasm. There are data, according to the Crimea relationship between these structures is not limited to contact, and described morfol. bonds between them. The nuclear envelope differs from other intracellular membranes in existence of a time in it — especially arranged sites of a cover. In these sites outside and internal membranes merge, forming the ringlet (annulyarny structure) limiting a time. In the field of ringlets the time is limited by 8 — 10 peripheral granules, and in the center of amorphous substance the central granule is located. Believe that granules are formed by the threads curtailed into a ball. Describe also side outgrowths and a diaphragm regulating pore sizes. The nuclear envelope is the main structure regulating Saturday exchanges between a kernel and cytoplasm. Through it RNA, RNP, histones, protamins, ribonuclease and some other macromolecules get. Substances about a pier. it is powerful (weight) St. 40 000 through I turf a cover do not get. Three main ways of transport of substances through it are possible: through a time (RNA, RNP), through a nuclear membrane (low-molecular substances), and also by emboly and protrusion of a nuclear envelope. The energy necessary for this transport is provided oxidizing phosphorylation (see), occurring in the cover.
Karyoplasm. The main part of nuclear contents consists of the chromatin weighed in nuclear sap. In live To. the karyoplasm looks homogeneous. During the fixing To. proteins of a karyoplasm coagulate owing to what the karyoplasm acquires setevidny structure with the small and large glybka of chromatin interspersed in it (the chromocenters, heterochromatin). In chromatin (see) systems of spiralizovanny microfibrils (individual chromosome threads) containing dezoksiribonukleoproteid (DNP-threads), and also large ribonukleoproteidny granules located on the periphery of chromatin are revealed. It is shown that the microfibrils making chromatin or consist of two DNP threads, or are one DNP sverkhspiralizovanny thread. Across Kornberg (R. D. Kornberg, 1974), each chromatinic thread represents a chain of the repeating units — the nucleosoma including apprx. 200 couples of the bases. The core of a nucleosoma — platisy is formed by an oktomer of 4 fractions of histones in the form of a disk (to dia. 11 nanometers, thickness are 5,7 nanometers). From outer side to platisy twists a superspiral of a double helix of DNA. In interchromatinic sites fibrilla and granules of RNP is found. Perikhromatinovy fibrilla, granules of RNP and material of the breaking-up kernel at the beginning of a mitosis concentrate on chromosomes, forming perikhromosomny RNA, edges serves as the beginning of a cycle of chromosomal RNA (see. Mitosis ). At many protozoa, in not sharing kernels of cells of sialadens of some dipterous insects (drosophila), etc. spiralizovanny chromosomes can be observed it is intravital.
At the heart of the ultrastructural organization chromosomes (see) the individual filaments described above formed by a double helix of DNA and the proteins histones connected with it lie. According to a hypothesis of the many and filamentous organization, the chromosome contains not less than 2 DNP threads.
On a hypothesis of folded thread of a chromosome are formed by one DNP coiled thread which, developing in cross and longitudinal folds, creates a chromatid; the last hypothesis is supported by most of researchers.
Comparison morfol, and cytochemical, features of structure of a kernel with the organization of chromosomes, and also formation from the last a kernel upon termination of process of division To. prove that the kernel is formed by individual filaments of chromosomes and products of their activity. Distinctions in structure of a karyoplasm at live and fixed To. are connected with different extent of spiralling (condensation) of DNP threads, with the changes of their optical properties and localizations caused by influence of fixers. At the same time these comparisons along with constant presence of spiralizovanny regions of chromosomes (heterochromatin, glybk of a sex chromatin) convince of firmness of the original position of genetics about a continuity of chromosomes. The chemical organization of a kernel is characterized by the high content of DNA, RNA, nuclear proteins (histones, or protamins, negistonovy proteins) forming nucleoproteids and a number of enzymes of synthesis and a transcription of DNA, and also enzymes of energy balance. The combination of a submicroscopy to chemical fractionation allowed to find out bases of chemical structure of a kernel. Ribosomopodobny granules of nuclear sap are formed by RNP, TRNK and soluble proteins; elementary microfibrils of chromatin and chromosomes consist of DNP (DNA, histones, negistonovy proteins); a nukleonema of a kernel — from RNP, negistonovy proteins; the nuclear envelope is formed by so-called residual proteins.
Kernel consists of 3 components: fibrilla, granules and amorphous matrix. The fibrillar component consists of the thin RNP-threads (nukleonem) connected with granules of RNP. A granular part is created by granules, between to-rymi the small number of threads is located. Distribution of both parts of a kernel varies in different To.: the fibrillar zone is more often located in the center, and granular — on the periphery. The ratio between these components depends on a functional condition of a kernel: at intensive synthesis of RNA a granular part prevails. The kernel is usually closely connected with okoloyadryshkovy chromatin, adjacent to it, threads to-rogo sometimes get in kernel (see).
The kernel performs genetic and metabolic functions. Both of these functions are defined by existence in a kernel of DNA and its properties. Preservation and self-reproduction of DNA, and also synthesis on its basis information, or matrix, are provided to RNA (MRNK) with the main nuclear enzymes (the DNA polymerase participating in DNA replication, and the RNA polymerase catalyzing synthesis of specific MRNK) concentrated in chromosomes. Genetic function of a kernel consists in transfer of hereditary information to again formed cells. It occurs during division To. by distribution of nuclear material (chromosomes) between affiliated To. The metabolic functions connected by hl. obr. with a transcription, are carried out by hromosomalny microfibrils (synthesis of MRNK) and a kernel (synthesis of ribosomalny RNA and assembly of predecessors of ribosomes). Believe that in a nuclear envelope there are processes of formation of makroergichesky phosphates and reaction of intermediate metabolism. Through a nuclear envelope nucleocytoplasmic interactions are carried out.
Possessing defined morfol. features and constantly being present in To., all organoids are characterized by participation in the all-cellular functions providing the main manifestations of life activity of K. S with them breath and accumulation of energy (mitochondrion), protein synthesis (ribosomes, a granular cytoplasmic reticulum), accumulation and transport of lipids and a glycogen (a smooth cytoplasmic reticulum), formation of products of synthetic activity and their secretion (Golgi's complex), intracellular digestion and protective function (lysosomes), etc. is connected. Organoids perform not one strictly bounded function, but usually participate in a number of various intracellular processes. So, the cytoplasmic reticulum participates in processes of protein synthesis and at the same time serves as circulator system K. In Golgi's complex along with formation of secretory granules synthesis of polysaccharides is carried out. Moreover, during the different periods of a life cycle To. function of some organoids can change. E.g., a cytoplasmic reticulum and a nuclear envelope during a mitosis vegetable To. carry out polarization of a spindle of division. Though separate organoids usually bear different functions, their specialization is not brought to strict monopoly of one organoid for this function. Any function K. is not result of activity of one organoid. Any manifestation of life activity To. — a consequence of the coordinated consecutive work of its interconnected components.
In some types K., in addition to all-cellular structures, still the metaplasmatic educations performing private, special functions are had. The tonofibrils performing basic function concern to them (To. a multilayer epithelium), the myofibrils, flagellums and cilia which are carrying out the movement K. (spermine, ciliary To., infusorians), educations on a surface To. (microvillis, a brush border), the absorptions participating in processes; the structures providing contacts between To. (desmosomes) in a metaphyte. Specialization leads to development of metaplasmatic structures To.
Inclusions — temporary educations To., which appear and disappear in the course of a metabolism. Distinguish trophic (proteins, lipids, a glycogen and pigments), secretory (secretory granules) and the specific inclusions connected with various special functions (leukocytes, melanocytes, corpulent To., etc.). Depending on their physical. states distinguish dense inclusions — granules (see) and inclusions with liquid contents — vacuoles (see. Vacuole ).
Features of a structure of a plant cell
the Structure vegetable To. it is similar to K. Odnako's animals vegetable To. have a number of features, in particular the thick cell wall, special organoids called by plastids, the most important of which are chlorolayers. In chlorolayers process is carried out photosynthesis (see), as a result to-rogo energy of a sunlight turns into the chemical energy reserved in To. Fundamental difference of vegetable organisms from animals is dominance at them synthetic processes over processes of energy release.
Vegetable To. has the rigid cellular cover surrounding and protecting a plasma membrane. It forms some kind of skeleton giving to vegetable fabrics mechanical strength. The cell wall consists hl. obr. from cellulose (see), formed most To., walls of the adjoining cells are cemented by pectin (see. Pectic substances ). In the course of growth and a differentiation To. a layer behind a layer also the tertiary covers which are waste product of cytoplasm are postponed primary, secondary, and sometimes.
The cell wall is crossed so-called. plazmodesmam (see) — bridges of cellular contents. Inside plazmodesm the thin plasma membrane continuously passes from one cell into another owing to what cytoplasm next To. it is reported. Such continuous communication provides intercellular circulation of the solutions containing nutrients, dissolved gases and other connections. Apparently, the similar mechanism compensates impossibility of active capture by a cellular membrane of the liquid environment (see. Pinotsitoz ) or solid particles (see. Phagocytosis ), characteristic of animals To. or To. protozoa.
A cytoplasmic reticulum vegetable To. has the same structure and performs the same function, as in K. Odnako's animals for vegetable To. extent of development of vacuolar system has bigger value. Apparently, synthetic activity To. leads to accumulation in tanks of a cytoplasmic reticulum of the soluble carbohydrates, proteins and pectins surrounded with a proteinaceous and lipidic membrane. These accumulations of hydrophilic connections represent rudiments of future vacuoles which in process of hydration of a cell grow and merge with each other, turning into vacuoles.
Golgi's complex at plants consists of the dictyosomes disseminated through cytoplasm. Dictyosomes and the related bubbles are especially numerous in To., producing slime (e.g., To. root Czech of a face of bean).
Mitochondrions in vegetable To. are constructed as well as poorly differentiated cells of a mitochondrion contain few cristas in animal K. V. In mitochondrions To., participating in process of photosynthesis, the number of cristas increases.
For vegetable To. existence of the plastids containing pigments (a chlorophyll and carotinoids) and capable to synthesize is characteristic, and also to accumulate storage compounds (starch, fats, proteins). Chlorolayers have special value. At their higher plants is to 20 — 40 (the size 4 — 6 microns) in one K. V the growing leaves chlorolayers breed division. One of the main chemical components of chlorolayers is chlorophyll (see) which, as well as pigments of an animal organism (hemoglobin and Tsitokhroma), contains porphyrias, but takes the place of iron in its molecule magnesium. Chloroplast has a double membrane. It is filled with a stroma, in a cut there are grana — the flattened little bodies, shaped the plates located columns. Plates gran are derivative an inner membrane of chlorolayers; exactly here the system of photosynthesis and electron transfer is localized. Chlorolayers have DNA and RNA differing from nuclear in which protein synthesis is carried out.
Features of a structure of unicells
In a structure and physiology of protozoa which are independent organisms are combined cellular and organismal lines. Electronic microscopic examination of a structure of protozoa confirms their cellular nature: they have the same cellular organoids, as To. metaphytes. Only the few protozoa (e.g., amoebas) have ability to change a shape of a body with formation of pseudopodiums, and the majority of protozoa has the constant form of a body, edges is provided with various structures, usually complex system of basic fibrilla (infusorian) or a pellicle (flagellates, infusorians, some Sporozoa); mineral skeletons of various chemical structure are very different and eurysynusic (foraminifera, radiolarias).
Cytoplasm of unicells can have different degree of a differentiation. Cytoplasm at infusorians is most differentiated. Idiosyncrasy of many protozoa (flagellates, infusorians) is existence of the organellas providing capture of food, digestion and other functions. In life of protozoa processes of osmoregulation, especially are important for fresh-water organisms.
Current of liquid through a body of the elementary is regulated by the sokratitelny vacuoles which are constantly present organella. The difficult differentiation is reached by forms of motion and motive devices. The simplest form is the amoeboid movement, it is much more difficult — the flagellar movement (see. Flagellates ).
Long time was considered that the kernel of many protozoa possesses more primitive forms of division, than a mitosis at To. metaphytes, however later it was proved, as at protozoa the mitosis with the DNA replication preceding it takes place.
To., being live complete system, supports and recovers the integrity, adapts to the changing conditions of the environment. At the same time To. grows, develops, performs various functions; end products of a metabolism, and also a part of the produced energy are allocated to the environment. All these manifestations of life activity To. are supported due to the synthetic processes proceeding in live To.
In a kernel animal To. molecule DNA represents linear (in bacteria and mitochondrions — ring) polymer, in Krom separate monomeric units are connected among themselves by means of phosphatic groups. Genetic information is written down on this linear molecule in the form of a certain sequence of heterocyclic bases: two pirimidinovy bases (see) — thymine (T) and a tsitozin (Ts) and two purine bases (see) — adenine (A) and guanine (G). DNA threads combine in a double helix, inside a cut of the basis connect hydrogen bindings in pairs: And — T and G — C. Each member of couple one chains is supplementing (complementary) to another. According to the principle of a complementarity, the sequence of nucleotides of one chain of DNA unambiguously defines the sequence of nucleotides in the second chain.
At replication of molecules DNA in process of untwisting of spirals the complementary bases join their bases by means of a DNA polymerase; and on two maternal threads of a spiral form two affiliated, in each of which one maternal thread, and the second «affiliated» (see. Replications ). In parallel with DNA also histones of chromosomes so the ratio of amount of DNA and histones in a kernel remains stable are synthesized.
Coded in DNA of a kernel animal To. information is usually used not at the same time: in molecule DNA are activated one, other sites, however the most part of DNA somatic To. is in an inactive state. Suppression (repression) of matrix activity of the respective site of DNA is carried out with the help histones (see) it is also regulated by special genes; morphologically such «switching off» is expressed in spiralling of the respective site of a chromosome. In reverse (i.e. derepressions of genes) a part is played by negistonovy proteins.
On a matrix of DNA macromolecules RNA, the main biol which function consists in participation in synthesis of protein by transfer of genetic information from a matrix of DNA on polypeptide chains under construction are synthesized. Synthesis of RNA on a matrix of DNA is carried out by the same principle, as replication of DNA threads, i.e. on a chain of DNA by means of a RNA polymerase is based RNA thread with the sequence of the bases, complementary in relation to DNA, with that feature that RNA include not thymine, as in DNA, and uracil and sugar a ribose instead of desoxyribose (see. Transcription ).
The ground mass of cellular RNA is made by high-molecular ribosomalny RNA, synthesis a cut is carried out on chromosome threads in a kernel then r PH K is transferred to cytoplasm where ribosomes form. Information (matrix) RNA makes 3 — 5% of all amount of cellular RNA; it is transcribed on triplets of nuclear DNA in the form of heavy polycisthrone chains which then break up to shorter chains and in a complex with protein are transferred to a cover of a kernel. During the passing through a cover of squirrels, connected with MRNK, remains in a kernel, carrying out a role of a carrier of other portions of MRNK. The nukleoproteidny particles of this sort serving as the MRNK temporary storage, G. P. Georgiev (1970) suggests to call informomer; Bernhard (W. Bernhard, 1972) presumably identifies them with perikhromatinovy granules.
Synthesis of protein on a matrix of MRNK, i.e. broadcasting (see), occurs on ribosomes. It is preceded by activation of the amino acids which are contained in cytoplasm. Molecules TRNK deliver the activated amino acids to ribosomes where amino acids combine a peptide bond, forming a polypeptide chain. When synthesis of a proteinaceous molecule comes to the end, the ready polypeptide chain is disconnected from ribosomes. The complexes of ribosomes combined by molecule MRNK during synthesis of polypeptides are called polysom. The important role in education and function of these complexes is played by proteinaceous factors of broadcasting (see).
The energy necessary for ensuring the life activity, To. receives from makroergichesky phosphatic connections at which hydrolysis a lot of energy is emitted. Treats these connections adenosine triphosphoric to - that (ATP), and also triphosphates of uridine, a tsitozin and guanine riboside (UTF, TsTF, GTF), creatine phosphate, phosphoenolpyruvic to - that, aminoacylacetates and an uridinfosfatglyukoz (see. Vysokoergichesky connections ). Accumulation of energy and formation of ATP is carried out in two ways: due to processes of oxidizing phosphorylations (see) in mitochondrions and less effective way glycolysis (see) in a hyaloplasma and a kernel To.
A life cycle and a reproduction of cells
the Life (cellular) cycle call the entire period of existence individual K. Period between divisions, during to-rogo To. keeps the issued kernel, call interphase. B this period in To. continuously the processes of synthesis of RNA and proteins providing a reproduction To proceed. and its preparation for a mitosis (autosintetichesky interphase), and also growth, differentiation and other functions K. (heterosynthetic interphase). In interphase often sharing To. (e.g., in the split-up ova) autosintetichesky processes prevail, and their life cycle in essence is a mitotic cycle. At the majority fabric To. in interphase, besides, heterosynthetic processes are carried out. Therefore in principle it is necessary to distinguish the concepts «cellular cycle» and «mitotic cycle» though the accurate criteria allowing to divide auto-and heterosynthetic processes, are not present yet.
Unlike continuous synthesis of RNA and proteins, synthesis of DNA is carried out only during a certain period of interphase, after a while after a mitosis and coming to the end in several hours prior to the following division. Proceeding from it, a life cycle To. divide into four periods: actually mitosis (M), presintetichesky period (G1), period of synthesis of DNA (S) and post-synthetic period (G2). At the same time conditions for synthesis of DNA exist during all interphase. In particular, during the periods of G1 and G2 reparative synthesis of DNA (correction of small distortions of the DNA code can be carried out at reduplication), for to-rogo a large number of predecessors is not required.
In G1 period MRNK and enzymes necessary for education of predecessors of DNA and providing DNA replication are synthesized. Apparently, MRNK which are required to start the S-period are generally synthesized during the Gj-period of the same cycle, shortly before the beginning of DNA replication, but a part of MRNK can pass from one cycle into another. Believe that stable matrixes of MRNK provide succession of processes in consecutive cycles whereas short-lived matrixes participate in synthesis of regulatory proteins at different stages of a cycle. Just before the beginning of the S-period in To. formation of proteins initiators of DNA replication comes to the end. In the S-period there is a replication of molecules DNA. G2 period is studied insufficiently; it is supposed that during this period there is a synthesis of ribonucleoproteins from which in a pro-phase the mitotic device forms, accumulation of energy resources comes to the end To., and also synthesis of the RNA and protein necessary for the introduction To. in a mitosis and passings of the period of G1. In a life cycle of some To. there can be no period of G1; in such To. conditions for initiation of doubling of molecules DNA are created prior to approach of a mitosis.
Such is the general scheme of a course of autosintetichesky processes of a mitotic cycle. Heterosynthetic processes of a cellular cycle are carried out in the period of G1; the delay time in heterosynthetic interphase is called dormant periods and designated G0 or R1 symbols for heterosynthetic processes in presintetichesky and R2 — in post-synthetic the periods. Being in dormant periods, To. on a number of properties differ from proliferating To., in particular special type of metabolism such «based» To. allows them to resist to adverse effects more successfully.
Considering that reduplication of DNA and formation of two-chromatid chromosomes occurs in the S-period of interphase I. A. Alov (1972) suggested to carry S-and G2 periods of a cellular cycle to a mitosis, having combined them under the name of a preprofaza.
Duration of a cellular cycle in general varies over a wide range depending on age, hormonal balance of an organism and other factors.
The processes providing preparation To. to a mitosis, in particular DNA replication in the S-period, in general are under control of the genetic device K. However a part of these processes can be regulated also by different ways, napr, the level of end products of reaction by the principle of a negative feed-back (extra genomic control). Among the factors regulating proliferation To., the great value is attached to tkanespetsifichesky intracellular inhibitors of proliferation — to chalones (see). The chalones which are selectively suppressing proliferation To are emitted., in various periods of a cellular cycle.
Essence mitosis (see) consists in the difficult transformations of a cellular kernel providing succession of chromosomes among cellular generations and emergence genetically equivalent affiliated To. In the course of mitotic division distinguish 4 main phases: professional azu, metaphase (stage of a maternal star), anaphase (stage of affiliated stars) and telophase.
By the beginning professional elements viscosity of cytoplasm increases and To. are rounded. Intensity of synthesis of protein considerably decreases, synthesis of RNA stops in a late pro-phase. Centrioles of the cellular center, reduplitsirovavshiyesya at the end of the previous mitosis or in interphase, begin to disperse to poles To.; between them forms consisting of microtubules to dia. 14 — 25 nanometers spindle of division; the fibrilla which is radially located around centrioles forms a peculiar figure like radiant shine (astrosphere). All these structures in total make the mitotic device K., necessary for implementation of the movement of chromosomes. By the end professional elements of a centriole are located at opposite poles To., the cover of a kernel collapses; kario-and cytoplasm merge. Duration professional elements in different To. from 2 to 270 min. fluctuate.
Move to stages of metaphase of a chromosome to the equator of a spindle in such a way that their centromeres are turned to the center, and shoulders — to K. Obrazovannuyu' periphery chromosomes call a figure the equatorial plate or a maternal star. By this time reaches full development a mitotic (akhromatinovy) spindle. After an attachment the centromere to hromosomalny threads of the mitotic device begins transition to the following stage of division, and sister chromatids are divided. Duration of metaphase — from 0,3 to 175 min. Separation of sister chromatids comes to the end at a stage of an anaphase. Two groups of chromosomes turned by centromeres to poles, and shoulders — to the equator are formed To. (so-called figure of affiliated stars). The site of a spindle between these groups is formed by interzonalny threads. Believe what in movement of chromosomes to poles plays a role both shortening hromosomalny, and lengthening of interzonalny threads of a spindle. Duration of an anaphase makes 0,3 — 122 min.
In a final stage of a mitosis (telophase) there is a reconstruction of affiliated kernels, destruction of the mitotic device and division of a body To. on two affiliated To. (process of a tsitotomiya or cytokinesis). In process of a despiralization and lengthening of chromosomes during early telophase synthesis of RNA is recovered, formation of a kernel begins. Formation of a cover of a kernel in the form of double membranes around each chromosome can begin in an anaphase; in telophase individual covers of chromosomes merge, forming covers of affiliated kernels. Tsitotomiya is usually carried out by emboly of a surface layer of cytoplasm and the subsequent relacing of a body of K. Inogd the tsitotomiya does not occur therefore the mitosis can come to the end with education two-or multinucleate cells. At division of a body To. the main structures of cytoplasm (organoids, inclusions) share between affiliated To. approximately equally. Compleche Golgi at the same time breaks up to separate dictyosomes (dictyokinesis).
A special form of division To. is meiosis (see). At meiosis there are two consecutive divisions as a result of which from diploid (2n) oocytes and spermatocytes of the 1st order ova and spermatozoa with a haploid (n) set of chromosomes (are formed see. Gametogenesis ). In a pro-phase of the first division homologous chromosomes combine in couples (so-called bivalents) which contain about 4 chromatids (tetrad). Parts of pair chromatids can cross, forming hiazma. By means of this process exchange of sites of homologous chromosomes — i.e. a recombination of genes is carried out (see. Recombination, chromosomes ). At the highest animals in an anaphase of the first division to poles To. departs on the whole chromosome from each homologous couple. After short interphase there comes the second division of meiosis, at Krom as at a usual mitosis, to poles chromatids of each chromosome disperse. 4 haploid kernels are as a result formed; in a male body from all four spermatozoa form (see. Spermatogenesis ), and in women's only one cell turns into egg; polar (napravitelny) little bodies are formed of other three (see. Oogenesis ). At fertilization of ova a diploid set of chromosomes is recovered.
Increase in cellular weight can be carried out also without division To. — by an endoreproduction. At one of types of an endoreproduction (an endomitosis, or an intranuclear mitosis) spiralling and division of chromosomes happen in the kernel which kept a cover, and sometimes and a kernel. In this case reduplication of molecules DNA proceeds as usual, in the S-period of interphase. After passing of G2 period in a kernel become visible under a microscope of a chromosome which pass a normal cycle of doubling and division (an endopro-phase, endometaphase) and again despiralizutsya in endotelophase in a kernel. At some fungi and the elementary at the same time in a kernel the «closed» mitotic device providing discrepancy of chromatids to poles of a kernel forms. As a result chromosome number in a kernel doubles, sometimes repeatedly, and there are polyploid kernels. According to increase in ploidy of a kernel the mass of cytoplasm increases and the colossal cells containing sometimes St. 1000 chromosomal complements develop. The endomitosis is widespread among nematodes, insects, cancroid, the elementary, in roots of some plants and so forth.
In particular, at infusorians the endomitosis leads to formation of a macronucleus.
Polyploidization To. the highest animals occurs so: To. from G2 period enters G1 period, grows, enters the next synthetic period etc. In a number of tissues of dipterous insects, at infusorians and at some plants similar processes can lead not only to a polysomia, as at the highest animals, but also to a politeniya, t. et to increase in quantity of chromonemas in chromosomes without increase in number of chromosomes and their superspiralling. Polytene chromosomes which can surpass in hundreds of times in the size usual are as a result formed. The nuclear mass and cytoplasms in To. increases according to increase of content of DNA. In specialized and differentiated To. the endoreproduction can lead to increase in weight To. without disturbance of specific cellular structures and without the termination of their functioning that is of great importance in fiziol. regenerations (see). To reveal a poliplodiya To. it is possible or on increase in content of DNA in kernels, a cut usually correlates with their sizes, or on polyploid mitoses.
V K. a row normal and patol, changed (e.g., malignant tumors) fabrics direct division of kernels often meets — amitotic division (see). This process can be carried out at any moment of interphase polyploid or diploid To. At amitotic division there is no spiralling of chromosomes, destruction of a cover of a kernel and formation of the mitotic device; in the beginning the kernel is extended and pereshnurovyvatsya, then also the kernel shares a relacing To. In certain cases in a kernel the partition — a nuclear plate is formed.
The question of full value of amitotic division as way of cell fission finally is not decided yet that it is substantially connected with a variety of types and lack of accurate morphological criteria of amitotic division. At generative amitotic division a kernel To. it is divided into two kernels of the identical size with the balanced content of DNA. It is possible in case of division of polyploid kernels though sometimes synthesis of DNA and doubling of volume of kernels happens during their direct division or right after it. As a result the surface of contact kario-increases and cytoplasms, metabolism polyploid is normalized To. also functionally full-fledged two-form - and
some fabrics direct division of kernels leads multinuclear K. V to education two-and a lot of nuclear To., capable as to further amitotic division of one or several kernels, and to division into one-nuclear K. V other cases the kernel is divided into unequal parts (meroamitoz, budding of kernels) or into several small unequal parts (fragmentation). These To., as a rule, perish (so-called degenerative amitotic division) though sometimes synthetic processes in them continue and kernels can reach a normal amount. Such degenerative amitotic division is observed in growing old To. with the dying-away vital signs; it, naturally, cannot be a form of a reproduction To.
Permeability. Phagocytosis. Pinotsitoz
Substances get in To. also leave it through a plasmolemma by means of various mechanisms. Distinguish the passive transfer going without energy consumptions and the active transfer going with the energy consumption reserved inside To. Passive transfer has the nature of diffusion of molecules of substances and ions. Active transfer — biological process, at Krom transfer of substances can be carried out against a gradient of concentration (see. Transport of ions ).
By active transport pass through a plasmolemma various mineral substances which concentration in the environment is lower, than in cytoplasm K., and also number of nonelectrolytes, first of all carbohydrates. The mechanism of such transport is studied insufficiently. Membrane theory permeability (see) connects it with euzymatic activity (enzymes carriers or permeaza) of various sites of a cover To. and their membrane potentials (see. Ionophores , Membranes biological ). According to the sorption theory of permeability the leading role is assigned to all mass of living material K. — solubilities of substance in protoplasm, to features of the adsorptive or chemical binding of these substances cellular colloids, etc.
Ability to absorption by some types of cells of various corpuscular particles (e.g., the motes, bacteria which died To. and their fragments) call phagocytosis (see). Depending on properties of an object and cell the taken particles or are digested (complete phagocytosis), or are not digested To. (incomplete phagocytosis). In the latter case fagotsitirovanny bacteria can keep the viability. Phagocytosis can be carried out or by invagination of a plasmolemma in the place of contact of an object with To., or by formation of the pseudopodiums enveloping a particle.
The capture of liquids and colloidal solutions proceeding in essentially similar way is called pinocytic (see). Pinotsitoz (fig. 7) plays a large role in penetration in To. macromolecular substances, first of all proteins. It is important also in transport of liquids through cytoplasm of an endothelium of circulatory capillaries.
The movement of cells
is Distinguished by three main types of the movement K.: movement by formation of locomotory ledges of cytoplasm (the amoeboid movement); the movement by means of cilia or flagellums; muscular contraction.
The amoeboid movement is peculiar to amoebas, macrophages, leukocytes and others To. or to the unicells deprived of direct mechanical connections with people around To. Formation of undulating membranes and various type of the pseudopodiums (a lobopodium, a filopodium, a rizopodiya, an axopodium) arising due to movements (currents) of cytoplasm is the cornerstone of this type of the movement. More or less fixed To. (fibroblasts, layers epithelial or embryonal To.) move by the sliding movement, at Krom currents of cytoplasm do not come to light, and undulating membranes differ in the small width (no more than 5 — 10 microns). At the movement extent of coupling of cells with substrate and among themselves is of great importance.
Normal, nemalignizirovanny To. at contact with each other stop the movement and in cellular cultures do not crawl at each other (contact inhibition). Sharply anaplazirovanny, atypical To. (To. sarcomas, cancer To., the signs of a fabric differentiation which lost everything, etc.) have reduced adhesive properties, contact inhibition at them is absent, and in cultures they crawl as at each other, and on normal To. These data are of a certain interest in connection with a problem of innidiation of malignant K.
Sushchestvuyut special organoids of the movement K. — cilia and flagellums. Cilia have rather small length and are located on a free surface To.; set of their movements allows infusorians to make difficult movements in fluid medium. In an epithelium of a number of bodies ciliary cilia meet; their movement plays an essential role in movement of liquids, dust particles, sex cells and so forth. Flagellums are longer than cilia; their movements are more difficult. By means of such flagellums spermatozoa move.
Cilia and flagellums represent plasmatic outgrowths to dia, apprx. 200 nanometers. Under a plasma membrane 9 couples of peripheral micro tubules, everyone apprx. 25 nanometers in dia longwise are located. The wall of a microtubule And consists from 13, and microtubules In — of 10 threads to dia. apprx. 5 nanometers. From a wall of a microtubule And to a microtubule In next vapors are directed ledges («handles») from protein of the dinein having ATF-aznoy activity. These «handles» carry out interaction of the next couples of micro tubules: due to energy of hydrolysis of ATP they cause the shift of microtubules leading to a beating of an eyelash or a flagellum. In an axial part there pass two central microtubules surrounded with the central layer. Flagellums of spermatozoa contain, in addition to the called structures, the spiral thread going on the periphery — a cortical spiral.
Peripheral microtubules are connected with a basal little body (a basal body, a kinetosome), subjacent each eyelash or a flagellum; the central microtubules come to an end slightly earlier (in an aksosoma). From a basal little body in depth of a row K. threads 80 — 100 nanometers thick depart; in ciliary To. these threads form the ciliate cone turned by top to a kernel. The ultrastructure of kinetosomes, cilia and flagellums is in many respects similar to a structure of centrioles of the cellular center.
Muscular contraction is carried out by means of myofibrils (see. Muscular contraction ). In cross-striped muscle fibers of a myofibril consist of two types of protofibrils: thin (to dia. 5 nanometers) and thick (to dia. 10 nanometers); the first consist hl. obr. from actin, the second — from a myosin; at interaction of these two proteins the complex — actomyosin which in the presence of ATP has ability to reduction is formed. Protofibrils of both types are connected among themselves by system of crossbridges. According to the theory of the sliding threads both types of protofibrils at reduction of a muscle as if are moved each other, being displaced on interfibrillar intervals. In smooth muscular To. protofibrils to dia, from 2 to 6 nanometers are found.
There are bases to assume that all types of the movement K. are carried out on a uniform biochemical, and submicroscopic basis. Confirm it, in particular, similarity of sokratitelny proteins in various To. and a role of ATP as main source of energy at implementation of different forms of motion To.
Differentiation and specialization of cells
Differentiation (differentiation) originally designated only formation of various types K. and fabrics in process of a metaphyte from an oospore. Began to understand acquisition as differentiation later To. specialized functions, connected with emergence in it of the structures providing performance of these functions.
Often differentiation To. it is in a varying degree accompanied by loss or restriction of its productive capacity. In some fabrics along with highly specialized (differentiated) To. during life of an organism remain To., capable to reproduction and the subsequent differentiation — so-called cambial elements. In nervous tissue and skeletal muscles of vertebrate animals at a certain stage of ontogenesis stocks of cambial elements are exhausted and natural losses of the high-differentiated neurons or muscular To. it can be compensated only by a hypertrophy of the remained elements.
Consider that the reason of differentiation To. consists in the deep and descended repression of certain sites of a genome with activation of other its sites. An important role in this process is played by differential antigens of a cover To., appearing as a result of activation of genes. In differentiated To. initial matrix opportunities of a genome can remain. E.g., at transplantation of kernels of somatic cells of an adult frog from the last tadpoles, and kernels of chicken erythrocytes in develop in denucleated ova To. the person in culture are capable to reactivation and resuming of protein synthesis.
The mechanisms defining hereditarily the fixed repression and activation of a considerable part of a genome To., are studied insufficiently. There are data that control over development and differentiation of an oospore is carried out by the organizational center — a zone of cytoplasm, in a cut a large number nucleinic to - t is concentrated. At later stages of development in processes of differentiation an important role is played by continuous interaction of a kernel and cytoplasm K., and also interference To. different type (cellular induction).
Aging and death of a cell
Ageing represents process of decrease in adaptation opportunities To. and an organism in general, increases in their sensitivity to adverse effects. Therefore with increase in age To. (or an organism) the probability of approach of death increases.
The majority To. after an initial undifferentiated stage and differentiation passes into an end-stage of aging. Only for some To. a metaphyte (neurons, skeletal muscles) life expectancy practically matches life of an organism, and their updating is carried out at the subcellular level.
During the aging To. degree of orderliness of their arrangement in fabrics decreases, variability of their sizes increases, the polyploidy often develops (or its option — a dvuyadernost), degree of permeability of a cover decreases To., matrix activity of nuclear DNA is suppressed. Quite often during aging To. separate organoids collapse and replaced. The important role in this process belongs to lysosomes (autofagosoma, cytolysosomes) in which the dying-off sites of cytoplasm (are isolated and digested see. Lysosomes ). In elements of nervous tissue, in a myocardium and other fabrics so-called pigments of wear collect. In the growing old cultures To. vacuolation of cytoplasm and accumulation of small lipidic drops is observed. Along with the destructive phenomena in growing old To. also adaptive processes directed to recovery of functions K develop.
A number of researchers considers that duration of existence To. it is determined by its genome. It is confirmed, in particular, by Heyflik's data (L. Hayflick, 1972) about restriction of number of divisions in development some small differentiated K. Silard (L. Szilard, 1959) connected aging To. with accumulation of mistakes in reading of genetic information at a reproduction of molecules DNA. According to the adaptation and regulatory theory of aging which is put forward by V. V. Frolkis (1975) in regulatory genes To. primary changes which lead to repression of one and activation of other genes To develop. From other internal causes of aging To. a certain significance is attached to reduction of a degree of dispersion of colloids of protoplasm, loss by them of water and electric charge (the phenomenon of a so-called hysteresis of protoplasm).
The known role in processes of aging To. play also disturbance of the regulatory mechanisms maintaining constancy of composition of blood and an intercellular lymph, decrease in level of a number of hormones (a growth hormone, gonadotrophins of a hypophysis), accumulation in a blood plasma of inhibitors of growth To. etc. (see. Homeostasis ). Eventually growing old To. are exposed to a necrobiosis, their structure is broken, and To. perish (see. Necrosis ).
the General cytopathology has the task studying morfol, and fiziol, mechanisms of pathology To. The main directions of researches in cytopathologies (see) concern studying of the most widespread lines of pathology To.: reactions to damage; disturbances of circulation of intracellular liquid; dystrophic processes; disturbances of defense reactions To.; disturbances of permeability of cellular membranes and surface of a plasmolemma; hypertrophic and atrophic processes; pathology of differentiation and growth To.; pathology of a reproduction To.; pathology of the movement K.; pathology of a kernel and genetic device K. (so-called chromosomal diseases); disturbances of bonds between To. etc.
On various the damaging influences To. can answer with the same reaction — paranecrosis (see), i.e. a complex of reversible changes in cytoplasm, in particular increase in sorption properties of cytoplasm, increase in its viscosity, shift of pH in the acid party etc. At the same time in reaction To. also the lines specific to the different damaging agents come to light. One of the most often found answers To. the disturbance of circulation of intracellular liquid leading to the general or partial hydration is. Carry to this type of pathology vacuolar dystrophy (see), napr, in To. a liver at an anoxia, ischemia, thyrocardiac hepatitis, etc. The numerous vacuoles filling at the same time To., form from expanded tanks of a cytoplasmic reticulum and the bulked-up mitochondrions. At the same time in To. there is an increase in water content, ATP and a glycogen. A peculiar form of vacuolar dystrophy is the balloon dystrophy arising, e.g., at long exogenous intoxication. Process of vacuolation To. in this case it is also connected with swelling of mitochondrions and a cytoplasmic reticulum, however it begins on the periphery To., is followed usually by pycnosis of a kernel (see. Pycnosis ) also is irreversible.
Disturbances of breath To. and the changes in mitochondrions which are their cornerstone (tsvetn. fig. 17) take place at the most various pathology. Mitochondrions — extremely labile component K. Reduction of number of mitochondrions (in To. a liver at diabetes, starvation and after radiation), their sizes (at an experimental scurvy, diphtheria and a myopathy) or at morfol, changes of this organoid is followed by disturbance of the energy balance To. Swelling of mitochondrions is observed after influence of various damaging agents and at a row patol, processes (in To. a myocardium at its hypertrophy, heart failure and ischemia, in To. kidneys at nefroza, in To. a liver at obturatsionny jaundice, etc.). Swelling of mitochondrions is expressed in increase in their volume, fragmentation and loss of cristas owing to what organoid turns into the bubble limited only to an outer membrane. In some cases it is observed myelinations of mitochondrions (at a myopathy or ischemia of a myocardium), expressed stratification of concentric plates at an outer membrane of organoid and followed by disturbance of an associativity of breath and phosphorylation. At vacuolar alteration of mitochondrions in their matrix small bubbles (vacuoles) appear.
One of the most common forms of disturbance of fabric metabolism is dystrophy, followed by excess accumulation in To. products of exchange which qualitatively or are quantitatively changed as a result of disturbance of enzymatic processes (see. Dystrophy of cells and fabrics ). Among the processes participating in development of characteristic changes To., it is possible to allocate: 1) infiltration (infiltration by cholesterol of an internal cover of an aorta at atherosclerosis); 2) the perverted synthesis (e.g., synthesis abnormal proteinaceous polisakharidnykh complexes of amyloid); 3) transformation (e.g., the strengthened transformation of fats and carbohydrates in proteins or on the contrary); 4) decomposition (e.g., disintegration of zhirobelkovy complexes of membrane structures parenchymatous To. myocardium). Infiltration is described To. substances of the different nature — proteins (mucoid dystrophy, keratinizations, an amyloidosis, hyaline infiltration, etc.), lipids (myelin dystrophy, deposits of cholesterol), and also polysaccharides, pigments, salts of calcium, iron etc. At diabetes of inclusion of a glycogen take a form large glybok, localized not only in cytoplasm, but also in a kernel, and not only in places of usual localization (i.e. To. a liver), but also in others (To. an epithelium of kidneys, a myocardium, leukocytes, etc.) where they are normal or do not meet, or they are not enough. At atherosclerosis note extensive deposits of granules and crystal plaques of cholesterol in an endothelium of vessels. Iron at its surplus in an organism is laid in the form of ferritin not only in erythroblasts, reticular, hepatic To., but also in an epithelium of intestines, an endothelium of capillaries, in To. kidneys and other parenchymatous bodies, and not only in cytoplasm, but also in a kernel. At disturbances of metabolism in bacterial To. there are accumulations of inorganic phosphate or metaphosphate (volutin).
Dystrophic processes are connected not only with infiltration To. products of metabolism, but also with a difficult complex of changes of intracellular organoids and interactions between them. Emergence proteinaceous dystrophy (see) it can be caused by disturbance of any of stages of protein synthesis (DNA — ► RNA — ► protein) owing to errors of coding (e.g., synthesis of abnormal hemoglobin at a sickemia), defects of a transcription or broadcasting. The essential role in developing of proteinaceous dystrophy belongs to ribosomes. Their number can decrease (at alimentary starvation, etc.), to increase (at infection with mycobacteria a tuberculoma) or activity can change them funkts. Alimentary proteinaceous insufficiency is followed by changes in morphology of a cytoplasmic reticulum. It or bulks up and breaks up to large vacuoles, or is fragmented on small bubbles. Quite often (e.g., at a lack of phenylalanine) there is a degranulation of a granular cytoplasmic reticulum to separation of ribosomes from membranes, myelination of the last and relative increase in a smooth cytoplasmic reticulum.
At fatty dystrophy (see), in addition to infiltration To. lipids, note premature destructive changes of a cytoplasmic reticulum and mitochondrions (e.g., at alcoholism). Disturbances of exchange processes To. often depend on structural changes of a plasmolemma, on disturbances of its permeability and mechanisms of active transport of some substances (e.g., damage of sodium «pump» at x-ray radiation). Great attention is drawn by changes of a nadmembranny layer of a plasmolemma and electric zeta-potential of a surface To., what is often noted in tumoral To. (see. Membranes biological ).
Hypertrophic and atrophic changes extend as to all To. (e.g., at a vicarious hypertrophy or at a muscular atrophy after denervation), and on its separate components (e.g., a hypertrophy of mitochondrions in myocardial To. at a hypertrophy of a myocardium, acute occlusion of coronary vessels or at long physical. loadings).
The frequent satellite of development patol, processes are disturbances of defense reactions To. (see. Immunity , Immunology ). Suppression of phagocytosis is described at various intoxications and a hypoxia. At some infections (e.g., the Toxoplasmosis of mice) macrophages are exposed to destructive changes, and their phagocytal activity almost completely is suppressed. In other cases (an inborn granulomatosis of children) there is only an incomplete phagocytosis: bacteria are englobed, but are not exposed to a lysis in connection with change of activity of proteolytic enzymes.
An important role in processes of life activity To. and their autolysis play lysosomes. A row patol, changes of their structure and function is described at various diseases. In particular, the inborn disturbances of synthesis of lizosomalny enzymes arising at a leukodystrophy of a brain, a gargoilizm, disturbances of carbohydrate metabolism take place; disturbance of formation of primary lysosomes at defects of development of a complex of Golgi (at starvation and avitaminosis E); disturbance of removal of lysosomes (at ionizing radiation, a constitutional hyperbilirubinemia, etc.); disturbance of accumulation of acid hydrolases in lysosomes (at nefroza, gepato a lentikulyarny degeneration, a siderosis); strengthening of an autophagy (at avitaminosis E, a hypopotassemia, hypoxemic dystrophy of a liver, etc.); strengthening of formation of residual little bodies (at ionizing radiation, a disease Teja — the Saxophone); increase in permeability of membranes of lysosomes and an exit in cytoplasm of lizosomalny enzymes (at avitaminosis E, action of ionizing radiation, etc.), etc.
A special problem of oncology is pathology of a tumor cell (see. Tumours ). Specific features tumoral To. (cellular atypia) are caused some funkts, and obshchebiol. deviations. Carry an exit to them such To. from under control of the systems regulating proliferation normal To., changes of ability to adhesion and to contact inhibition (influence of contacts on the movement and division To.), and also increase in intensity of glycolysis and big variability of number and forms of chromosomes. These deviations try to connect with change of a surface cancer To. (reduction of number of desmosomes, increase in permeability for glucose) and their lizosomalny membranes.
Pathology of a reproduction To. meets not only at carcinogenesis (see), but also at other patol, processes (a radial illness, a viral infection, etc.). Disturbances of a normal current of a mitosis and the wrong distribution of chromosomes between affiliated To. lead to emergence To. with an unbalanced karyotype. Allocate three main types of disturbances of process of a mitosis: the pathology connected with damage of chromosomes (disturbances of spiralling and a despiralization of chromosomes, early separation of chromatids, fragmentation and spraying of chromosomes, formation of bridges, lag of chromosomes at the movement, not discrepancy of chromosomes, their swelling and adhesion); the pathology caused by damage of the mitotic device (a delay of a mitosis in metaphase, a kolkhitsinovy mitosis, dispersion of chromosomes in metaphase, multipole, monocentric and asymmetric mitoses, three-group and hollow metaphases); pathology of disturbance of a cytokinesis. Increase in mitotic activity, considerable increase of number patol, mitoses and delay of a current of metaphase — typical feature of a precancerous hyperplasia and cancer.
Pathology of kernels To. (coagulation of chromatin, a chromatolysis, etc.) leads to profound changes of all cytoplasmatic structures, to disturbance of synthetic processes in To., and then and to her death (see. Necrosis ). Emergence patol, intranuclear inclusions and the damage of a nuclear envelope which sometimes is followed by separation of fragments of a karyoplasm from it is also caused by deep disturbances of life activity To. The special attention is drawn chromosomal diseases (see), i.e. a number of the diseases and defects of development connected with damage of chromosomes. Their development is caused or dot mutations (see. Mutation ), or changes of number and structure of chromosomes (see. Chromosomal complement ). The diseases connected with changes in quantity and a ratio of gonosomes are fullestly studied (Klaynfelter's syndromes, Turner, a trisomy on X-chromosome).
Patol, processes in To. depending on character and depth come to the end or recovery of structure and function K. (intracellular regeneration), or her death (necrosis). At a necrosis or necrosis there is self-digestion To. (see. Autolysis ), what is connected with release of hydrolases from the damaged lysosomes. At the same time note profound changes of a plasmolemma which are shown or in separation from it of numerous bubbles, or in an otshnurovyvaniye of cytoplasmatic fragments (so-called plazmatoz). Products of a necrosis of cells can become autoantigens (see), causing development of autoimmune reactions. At development of a partial necrosis the perishing part K. it is delimited from viable sites by a demarcation membrane. Often perishing part K. has an appearance of the dense, large little bodies lying in cytoplasm (Mallori's little bodies, etc.). Necrobiotic processes in a kernel are expressed or in coagulation of chromatin and its transformation into the homogeneous basphilic weight (pycnosis), or into its vacuolations, reduction of amount of chromatin (chromatolysis) and, at last, in full dissolution (karyolysis). A necrosis, unlike a paranecrosis, irreversible process.
Virus cytopathology studies patterns of structural changes and function K., arising in the course of interaction To. with infectious or oncogenous viruses. This form of pathology To. it is generally connected with the fact that in To. there are new generations of mature virus particles (virions), and itself To. perishes. A complex of specific changes in the cellular cultures which are directly connected with reproduction of a virus in To., call cytopathic (cytopathic) effect; it differs from cytotoxic effect of viruses first of all in the fact that the last is not connected with replication of a virus and is deprived of specificity and the characteristic sequence patol, K. Neredko's changes it is possible to establish connection of toxic action of viruses with the abortal infection which is not leading to reproduction of a virus. Separate lines of cytopathic effect can be observed also without reproduction of a virus, e.g. at introduction in To. the virus inactivated by an ultraviolet light or during the processing To. ftorfenilalaniny.
To., in a cut this virus is capable to be reproduced with development of specific cytopathic changes, call sensitive (susceptible), and the virus capable to cause these changes, call cytopathic for these K. Tsitopatogennost of a virus is defined by features of metabolism To. also it is coded by its genome; for a number of viruses of the person connection of cellular sensitivity to them is established with this or that chromosome human To. E.g., according to V. D. Solovyov, Ya. E. Hesin and A. F. Bykovsky (1978), in a chromosome 19 genes of sensitivity to viruses of poliomyelitis, in a chromosome 3 — to a virus of herpes, in a chromosome 21 — to viruses Koksaki V.
Pronikaya in sensitive are localized To., nucleinic to - you viruses become a source new for To. genetic information also pervert her metabolism. The possibility of development of this process depends on three groups of factors: a) existence on a surface of a virus and To. specific receptors necessary for adsorption of a virus; b) existence in To. systems of the enzymes capable to deproteinize a virus, or conditions for synthesis of the corresponding fermental systems; c) existence in To. conditions and energy resources for development of a virus. V. D. Solovyov, Y. G. Balangding (1973) in the presence of these conditions in interaction of a virus and To. allocate three periods: 1) initial (adsorption of virions on a cover To., penetration of a virus in To. and deproteinization of a virus genome); 2) average, or an eklips-phase (protein synthesis, actually cellular macromolecules oppressing synthesis and providing replication nucleinic to - you a virus with the subsequent biosynthesis of components of a virus); 3) final (formation of virions and their exit from To.).
Deprived of fibrous casings virus nucleinic to - you are capable to cause infectious process even in insensitive to this virus K. In this case the formed affiliated virions are not capable to get into the people around which are not infected To., and development of an infection is limited to one cycle of a reproduction of a virus. Morfol, manifestations of cellular reaction are found only after synthesis of proteinaceous components of a virus that indicates an important role of the last in development of cytopathic changes
by K. Pervy morfol, manifestation of inversion of metabolism infected To. the dezintegrativny swelling of kernels revealed by means of a kariometriya serves.
Changes To. during the average period it is possible to find at cytochemical and electronic microscopic examination. During this period the normal sequence of stages of a cellular cycle is broken that is reflected in emergence of various aberation chromosomes (see. Mutation ), in change of a mitotic cycle, etc. In some cases mitotic division obviously infected To is observed. These changes precede development of actually cytopathic effect which develops in the final period and the hl is connected. obr. with formation and escaping To. virus particles.
Morfol, a picture of cytopathic effect depends on properties of the developing virus, on features infected To. and from conditions of an infection (structure and pH of culture medium, temperature, concentration of virus particles, age To., plurality of an infection, etc.). Depending on these factors full destruction can develop To. (tsitotsidny action of viruses), the strengthened reproduction infected To. (cytoproliferative action of viruses), transformation To. and so forth. A special form of destruction To. the immune cytolysis which is observed at action on infected with a virus K is. antiviral antibodies (humoral and immune cytolysis) or immune (effector) lymphocytes (cellular and immune cytolysis).
In the course of a viral infection the submicroscopic organization K changes.: membranes are modified, cellular organoids hypertrophy or collapse, new intracellular structures form (tsvetn. fig. 12, 13). An important role in initiation of these changes is played by virusospetsifichesky proteins. Some viruses during cytopathic action cause formation in To. the peculiar structures seen by means of the light microscope — virus inclusions. In relation to dyes virus inclusions divide on oksi-and basphilic; on chemical structure — on the containing RNA, DNA or deprived nucleinic to - t; on structure — on homogeneous and granular; on localization — on cytoplasmatic and intranuclear. In development of an infection the structure and chemical structure of inclusions can change. One types of inclusions (e.g., Guarniyeri's little bodies at infection with viruses of group of smallpox, intranuclear adenoviral inclusions) represent zones of maturing of virions inside To. (tsvetn. fig. 10 and 11), others are morfol, manifestation of defense reactions To, napr, oxyphilic inclusions in To. (tsvetn. fig. 9), third do not contain virus particles and are one of forms of reactions To. to development of a virus in it. Different types of inclusions are of great importance in differential diagnosis.
A number of the viruses relating to various systematic groups is capable to cause development in infected To. structures like simplast (simplastoobrazuyushchy viruses). Most often these structures arise due to merge To. owing to destruction of their covers in the field of intercellular contacts. Similar simplastoobrazuyushchy activity of viruses is, as a rule, combined with their hemolitic activity: high-hemolitic virus strains have also high simplastoobrazuyushchy activity. Usually formation of simplast is preceded by intracellular reproduction of a virus, but some viruses (e.g., parotitis, Sendai) the enzymatic activity cause an early simplastoobrazovaniye. Introduction to cultures To. the inactivated virus Sendai is received by heterokarionums — much nuclear To., formed by merge To. from animal different types or classes and used, in particular, for mapping of chromosomes (see. Chromosome map ).
A special form morfol, changes To. is it neoplastic transformation under the influence of oncogenous viruses, as a result a cut in To. the genetic changes leading to changes of metabolism, loss of ability to contact inhibition, acquisition of ability to accrescence and reproduction, change of antigenic properties, etc. develop.
According to the virusogenetichesky theory of L. A. Zilber the reason of these phenomena integration of a virus genome (in whole or in part) with a genome serves To. and induction of mutations To. At an infection the RNA-containing oncogenous viruses (oncornaviruses) a big role in these processes, according to Thymine and Midzutami (H. M of Temin, S. Mizutami, 1970), the return transcriptase (revertaza) — the enzyme of a virus providing synthesis of DNA on a matrix of RNA plays.
At the heart of viral diseases of the person and animals changes sensitive lie primary patol, To. organism. These changes can be similar to defeats To. cultures of fabrics (Guarniyeri's little body in a skin epithelium at infection with viruses of group of smallpox, colossal cells of Uortin — Finkeldey in an adenoid tissue at a clumsy infection), but can differ from them (development oksi-and basphilic inclusions in kernels of the neurons struck with a poliomyelitis virus). In a complete organism morfol, a picture of the developing changes To. is complicated by development inflammatory and immunol, reactions to virus proteins and the changed antigenic properties affected with a virus K. Therefore the patterns received in experiences on fabric cultures should be extrapolated on To. bodies and body tissues with care.
Bibliography: Alov I. A., Braude A. I. and Aspiz M. E. Fundamentals of functional morphology of a cell, M., 1969; Blyumkin V. N. and Zhdanov B. M. Influence of viruses on the chromosomal device and cell fission, M., 1973, bibliogr.; In an er-bank of E. M. Istoriya of the doctrine about a cell, M., 1970; Gerdon Dzh. B. Regulation of function of genes in development of animals, the lane with English, M., 1977, bibliogr.; D e P about-bertis E., Novinsky V. and With and e with F. Cytobiology, the lane with English, M., 1973; Yepifanova O. I., Terskikh V. V. and Zakharov of A. F. Ra-dioavtografiya, M., 1977, bibliogr.; Zussman M. Developmental biology, a per ~ with English, M., 1977; Ivanitsky G. R., Krinsky V. I. and Selkov. E. Mathematical biophysics of a cell, M., 1978, bibliogr.; Ingram B. M. Biosynthesis of macromolecules, the lane with English, M., 1975; Iostkh. Physiology of a cell, the lane with English, M., 1975; The Cellular cycle, under. edition of O. I. Yepifanova, M., 1973; Kosheva Yu. V., Lezhnev E. And. and Makarova O. P. Intravital morphometry of cells, M., 1977, bibliogr.; Levi A. and Sikevitsf. Structure and functions of a cell, the lane with English, M., 1971; Ney-fakh A. A. and Timofeev M. Ya. Molecular biology of developments, M., 1977, bibliogr.; Palikar And. Elements of physiology of a cell, the lane with fr., L., 1977, bibliogr.; V. V. sirs and V. S Spiders. Ultrastructural pathology, M., 1975; T e r c and M. Genetika and a zooblast, the lane with English, M., 1977; Truman D. Biochemistry of a cellular differentiation, the lane with English, M., 1976, bibliogr.; Ueili U. Apparat Golgi, the lane with English, M., 1978, bibliogr.; F and - N of e and N D., Kolmenr. imichell River. Membranes and their functions in a cell, the lane with English, M., 1977, bibliogr.; F r e y-Vissling And. A comparative orga-nellografiya of cytoplasm, the lane with English, M., 1976, bibliogr.; Harris G. A kernel and cytoplasm, the lane with English, M., 1973; X e with and Ya. E N. Sizes of kernels and functional condition of cells, M., 1967; Chentsov Yu. S. and Polyakov V. Yu. Ultrastructure of a cellular kernel, M., 1974, bibliogr.; BasergaR. Multiplication and division in mammalian cells, N. Y. — Basel, 1976; The cell in medical science, ed. by F. Beck a. J. B. Lloyd, v. 1, L. — N. Y., 1974; With h e v i 1 1 e N. F. Cytopathology in viral diseases, Basel and. lake, 1975; Goodwin B. C. Analytical physiology of cells and developing organisms, L., 1976, bibliogr.; Langley L. L., T e 1 f o r d J. R. a. Christensen J. B. Dynamic anatomy and physiology, N. Y., 1974.
I. A. Alov, I. E. Hesinonim