NEUROGLIA

From Big Medical Encyclopedia

NEUROGLIA (grech, a nerve + glia glue neuron; synonym glia) — one of components of nervous tissue in a head and spinal cord including the cells of various origin which are closely connected with nervous cells and their shoots and carrying out basic, trophic, protective and some other functions, and also the emergence playing a part in processes, transfers and carrying out nervous impulses.

History

the Term «neuroglia» was offered in 1846 by Virkhov who for the first time found the special star-shaped and spindle-shaped cells covering walls of ventricles of a brain and the central channel of a spinal cord. The big contribution to a research of a structure of N. was made by Deyters's works (O. F. Page of Deiters, 1865), Veygerta (To. Weigert, 1895), S. Ramone-and-Kakhalya (1913), Ortega (P. del Rio Hortega, 1919, 1921), A. I. Smirnova (1935), M. M. Aleksandrovskoy (1950), A. P. Avtsyna (1967), etc. Detailed studying of a thin structure of N., it fiziol, and biochemical, features began in the 60th 20 century in connection with implementation in practice of scientific research of methods of a submicroscopy, gisto-and radiochemistry, out of - and intracellular assignment of bioelectric potential etc. Nevertheless many questions concerning fiziol, values H. in activity of a nervous system and also biochemical, the processes proceeding in N. remain not studied.

The morphology

the Neuroglia consists of two genetically different types: macroglias, among cells a cut distinguish astrocytes, oligodendrocytes both epen-dimotsita, and microglias, cells call a cut glial macrophages or microgliocytes. Nek-ry researchers consider cells satellites gangliyev V.n.s, and neurolemmocytes of peripheral nerves as a peripheral Neuroglia. (see. Ganglion , Nerve fibrils ).

Astrocytes develop in the course of an embryogenesis from the epithelial cells of a neurotubule forming spongioblasts, to-rye turn into neuroblasts, and then into astrocytes. Oligodendrocytes have also ectodermal origin. They pass a stage of an oligodendroblast in the development. From epithelial cells of a neurotubule also ependimotsita develop. Glial macrophages are mesodermal elements since form from the histiocytes of a soft meninx migrating in a brain along walls of vessels.

The developing cells of a microglia are called mezoglioblasta.

Fig. 1. Diffraction pattern of bark of big cerebral hemispheres: a protoplasmatic astrocyte, adjacent to a nervous cell (1); 2 — a kernel of an astrocyte; X 14 000.
Fig. 2. Diffraction pattern of bark of big cerebral hemispheres: a plasmatic astrocyte among shoots of nervous cells; 1 — a kernel of an astrocyte, 2 — cytoplasm, 3 — shoots of nervous cells; X 23 500.
Fig. 3. Diffraction pattern of bark of big cerebral hemispheres: fibrous astrocyte; 1 — a kernel of an astrocyte. 2 — cytoplasm, 3 — fibrilla; X 23 500.

Astrocytes (synonym: astroglia, entogliya, classical glia). On localization distinguish the plasmatic astrocytes located in close proximity to a body of a nervous cell (fig. 1), designated as satellites (satellites) of a nervous cell, and fibrous astrocytes. The last can be among shoots of nervous cells (fig. 2 and 3).

Astrocytes — small cells of a star-shaped or spindle-shaped form, diameter of a body to-rykh 8 — 15 microns. Apply special methods of coloring to a svetooptichesky research of astrocytes: zolotosulemovy (according to Ramone-and-Kakhalyu), impregnation by silver (by Golgi's methods, Bilshovsky — Groce — Lavrentyeva). Shoots of astrocytes reveal also by means of methods of coloring across Snesarev, Veygert, etc. Kernels of astrocytes reveal the coloring applied to survey methods of a research of c. N of page (krezil-violety, toluidine blue, hematoxylin etc.).

At a svetooptichesky research astrocytes have larger kernels in comparison with oligodendrocytes and glial macrophages. Kernels of astrocytes of an oval form, light-are painted, contain small chromatinic grains. The kernel is usually badly expressed. In cytoplasm gliosomes (mitochondrion) come to light and fibrilla (see). The thin numerous shoots lasting in all directions depart from a body of an astrocyte. So-called vascular legs * are characteristic of astrocytes to-rye contact to basal membranes of capillaries.

Plasmatic astrocytes of shoots have more, than at fibrous, and they branch more often; fibrous astrocytes have longer and less branched shoots. The shoots of astrocytes contacting among themselves create on the surface of bark of big cerebral hemispheres under a soft meninx a thin gentle coat — an outer glial boundary membrane. Shoots of astrocytes form also thin coat at walls of cerebral cavities.

For electronic microscopic examination of an astrocytic glia drug fix by perfusion of a brain solutions of a glutaraldegid with the subsequent immersion it in osmium tetroxide.

Electronic microscopically astrocytes are characterized by the light electronic and transparent cytoplasm containing rather small number of organellas. The body of astrocytes has an uneven contour and as if repeats outlines of axons and dendrites, adjacent to it. At the majority of astrocytes cytoplasm rather big on volume; less often astrocytes meet, at to-rykh cytoplasm surrounds a kernel only with a narrow rim. Large roundish pl oval kernels have no the expressed skladchatost; chromatin (see) kernels forms small accumulations at a nuclear membrane, and also it is scattered diffuzno in the form of small glybok in a karyoplasm. In cytoplasm of plasmatic astrocytes elements of a cytoplasmic reticulum are very poorly developed: the granular network is presented by single short tubules, agranular network — accumulations of not numerous small bubbles and vacuoles. In cytoplasm, in addition to mitochondrions, more or less evenly located few polycatfishes come to light, occasionally meet lysosomes (see) and osmiofilny bodies.

Distinctions between plasmatic and fibrous astrocytes especially clearly are visible at electronic microscopic examination. Numerous bunches of fibrilla (thickness of each fibrilla of 8 — 9 nanometers) are characteristic of fibrous astrocytes, to-rye both bodies of a fibrous astrocyte, and its shoots (fig. 3) are located in cytoplasm. Fibrilla is presented to Svetoopticheski by uniform structure whereas at a submicroscopy comes to light that separate fibrilla is formed by bunches of microfibrils. It is proved that fibrilla is the singular intracellular elements performing specific functions. In process of thinning of shoots and removal them from a body of a cell the amount of fibrilla gradually decreases. Fibrilla is distributed in shoots of astrocytes unevenly, nek-ry shoots, rather small on diameter, may contain numerous fibrilla.

In shoots of plasmatic astrocytes single mitochondrions meet. Unlike axons, dendrites and shoots of oligodendroglyocites shoots of astrocytes have an uneven contour — they as if fill space between shoots of nervous cells.

According to Wolff (J. Wolff, 19G3), astrocytes make 45 — 60% of volume of gray matter of a brain. In c. there is no N of page actually intercellular space; the hmezhd> has densely located shoots of nervous cells and N.'s cells filling space between nervous cells only cracks width apprx. 20 nanometers. In a brain of the adult, according to Shlotts (Shlotz, 1959), is apprx. 150 — 200 billion cells of N. that more than by 10 times exceeds number of nervous cells.

Fig. 4. Diffraction pattern of bark of big cerebral hemispheres: the shoots (1) of astrocytes contacting to a surface of a capillary (2); x 14 000.

The Perikapillyarny space, according to electronic microscopic examination, is filled with shoots of astrocytes (fig. 4). Shoots of astrocytes cover more than 85% of a surface of capillaries, quite often they are located near synapses; large shoots contact to bodies of nervous cells. Specialized contacts of type are described desmosomes (see) both between the next cells of N., and between glial and nervous cells. These contacts are, apparently, places of the most active metabolism of ions.

Oligodendrocytes (synonym: the oligoglia, an oligodendrogliya) represent smaller, than astrocytes, roundish cells (to dia, apprx. 7 — 10 microns) with a small number (2 — 3) thin shoots, to-rye last on insignificant distance from a body of a cell. Oligodendrocytes have the round or oval kernel rich with chromatin. In a narrow rim of cytoplasm there is rather large number of organellas» Poverty shoots, apparently, and formed the basis for the name of these cells (oligo — small). During the coloring of cuts of nervous tissue cresylic violet oligodendrocytes are more often - all come to light as cells satellites of large neurons (perineyronalny). Oligodendrocytes are located in gray matter of a .mozg near accumulations of myelin fibers (perifastsikulyarny); in white matter of a head and spinal cord they quite often last a chain among bunches of nerve fibrils (interfastsikulyarny).

Fig. 5. Diffraction pattern of bark of big cerebral hemispheres: an oligodendrocyte, adjacent to a nervous cell; 1 — a kernel of a nervous cell, 2 — a kernel of an oligodendrocyte; x 14 000.
Fig. 6. Diffraction pattern of bark of big cerebral hemispheres: an oligodendrocyte with a large number of organellas in cytoplasm; 1 — a kernel of an oligodendrocyte, 2 — cytoplasm with high degree of an osmiofiliya; x 27 500.
Fig. 7. Diffraction pattern of bark of big cerebral hemispheres: an oligodendrocyte, adjacent to a nervous cell; 1 — a kernel of an oligodendrocyte, 2 — a nervous cell; x 14 000.

The electronic microscopic examinations conducted by Peyli (Paley, 1958), Hartmann (J. E. Hartmann, 1958), Shultts, Piz (Schultz, Pease, 1959), Peters (A. Peters, 1960), A. L. Mikeladze and E. I. Dzamoyeva (1970), added the characteristic of oligodendrocytes. In comparison with astrocytes they have the big electron density of a kernel and cytoplasm, in cytoplasm of oligodendrocytes numerous polysom are visible and ribosomes (see), small mitochondrions, microtubules, the granular and agranular network is rather well developed, lipidic inclusions meet. Unlike astrocytes in cytoplasm of oligodendrocytes there is no fibrilla. Bodies of oligodendrocytes have more correct rounded shape and more equal contour, than astrocytes (fig. 5 — 7).

Depending on degree of electron density of cytoplasm and a karyoplasm oligodendrocytes divide into three look: light, more osmiofilny and intensively osmiofilny. According to etikhm also nek-ry distinctions in their ultrastructure, especially in ultrastructure of a kernel are observed. Light oligodendrocytes with moderately electronic and dense cytoplasm have a light kernel with an electronic and transparent karyoplasm, a small amount of the melkogranulyarny chromatin which is rather evenly distributed on a karyoplasm, to-ry, however, forms small accumulations at a nuclear envelope. Kernel of such cells usually small. Oligodendrocytes with such kernels more often are cells satellites of large neurons.

More osmiofilny oligodendrocytes have a roundish or oval kernel, is frequent with an uneven contour, containing large glybk of chromatin, to-rye are located not only near a nuclear membrane, but also in a distance from it.

Intensively osmiofilny oligodendrocytes are characterized by an osmio-filny karyoplasm, indistinctly expressed kernel and the expressed electronic and dense cytoplasm. At oligodendrocytes with osmiofilny cytoplasm the quantity the policy increases.

In light oligodendrocytes mitochondrions, single tubules of granular network, few polycatfishes are visible that reminds ultrastructure of astrocytes.

Ependimotsita form a tight coat of the cellular elements covering the spinal channel and all ventricles of a brain. On the ultrastructure they are similar to other cells of a macroglia (see. Ependyma ).

Microgliocytes (synonym: glial macrophages, a microglia, mesoglia, Ortega's cells) as special type of cells were described by Ortega in 1919. They represent small cells (diameter of a body of cells apprx. 5 microns). The best gistol, method for identification of microgliocytes is impregnation by silver carbonate. The kernels of these cells which are intensively painted the main dyes (see. Basophilia ), have the irregular triangular or extended shape and are rich with chromatin.

Fig. 8. Diffraction pattern of bark of big cerebral hemispheres: 1 — a kernel of a microgliocyte, 2 — cytoplasm of a microgliocyte; x 33 000.
Fig. 9. Diffraction pattern of bark of big cerebral hemispheres: a microgliocyte with high degree of an osmiofiliya; 1 — a kernel of a microgliocyte, 2 — cytoplasm; X 25 000.

Not numerous, twisting shoots, the localized hl are characteristic of microgliocytes. obr. near capillaries. According to electronic microscopic examination, these cells have a small amount of cytoplasm, several short shoots (fig. 8). N., characteristic of cells, of this type is that their kernels and cytoplasm are intensively impregnated by various dyes applied both for light and for a submicroscopy. Therefore microgliocytes at electronic microscopic examination especially clearly are distinguished from other elements of tissue of brain with high degree of an osmiofiliya and electron density (fig. 9).

Physiology

N.'s Cells along with vessels of a brain and a meninx form a stroma of tissue of brain. Closely connected with bodies and shoots of nervous cells, N.'s cells provide not only basic, but also trophic function: The N participates in ensuring metabolism nervous cell (see). N.'s cells englobe decomposition products of nervous cells. Astrocytes with a vascular leg provide communication of nervous cells with a blood-groove. Astrocytes participate also in ensuring function of preservation of a homeostasis, they the first react to various changes of water-salt balance, supporting by that constants of water and electrolytic exchange.

The main function of oligodendrocytes — formation of a myelin in a nervous system and maintenance of its integrity (see. Myelination ). Oligodendrocytes take part in ensuring metabolism of nervous cells what the experiences indicating interdependent changes of metabolism of neurons and oligodendroglyocites testify to. At a considerable funkts, loading around nervous cells the number of their cells satellites considerably increases, reactive changes of neurons are followed by the expressed changes of a perineyronalny glia.

Glial cells satellites (astrocytes and oligodendrocytes) play an important role in ensuring specific functions of nervous cells. Sensitivity of neuroglial cells to ionic environmental changes considerably exceeds sensitivity of neurons. It is caused as high activity of glial Na + - To + - dependent ATP-ase, and more high-permeability of a membrane of cells of N. for potassium ions. The potassium ions leaving neurons or axons in a phase of repolarization easily get through membranes of cells of N., causing their depolarization. At the same time there is an activation of metabolism in N. Ustanovleno's cells that strengthening of potassium in the environment activates synthesis of amino acids and proteins in cells of a brain. At the same time exchange shifts in N. come much earlier and are expressed more than in neurons. At excitement of neurons in them the content of RNA, protein increases and activity of respiratory enzymes while the content of RNA and protein in nearby glial cells decreases increases.

The main function of microgliocytes is phagocytosis (see), though other cells of N. participate in this process.

An important indicator fiziol, activity of cells of N. is their electric activity. Membrane potential of cells of N. is much higher than the membrane potential of nervous cells. So, at vertebrate animals the membrane potential of cells of N. apprx. 90 mV, and the level of membrane potential of nervous cells is ranging from 60 to 80 mV. As N.'s cells have low-permeability for all ions, except potassium ions, the high level of membrane potential of its cells is defined by concentration of cations of potassium in cytoplasm (to 110 mmol). Other feature of electric processes in N. is that unlike the neurons answering action of various irritants with the local or extending processes in the form of spayk, N.'s cells answer only with gradualny, slow wavy changings <of urovyamembranny potential. N.'s depolarization (i.e. decrease in membrane potential) develops slowly, reaches a maximum in time of 50-500 ms up to 4 — 5 min.: the size of depolarization depends on the initial level of membrane potential. Initial level of membrane potential is also reached slowly, passing through a stage of hyperpolarization. Thus, excitement of nervous cells (more precisely, a certain population of nervous cells) is followed by N.'s depolarization in this site of c. N of page. N.'s repolarization (i.e. process of recovery of initial level of membrane potential of cells of N.) reflects the process of clarification of intercellular space from potassium ions (they are allocated at excitement of nervous cells) happening with the assistance of N. Odnovremenno N.'s cells removal of surplus of the neurotransmitter released by the synoptic terminations is made.

The N plays an important role in integrative activity of a brain. She takes part in mechanisms of formation of conditioned reflexes, dominants. According to A. I. Roytbak, establishment of new forms of temporary bonds happens to N.'s help, edges myelinizes «potential» synoptic bombways and transfers them to «urgent».

V. S. Rusinov and sotr. showed that formations of temporary bonds are the cornerstone electrotonic forms of the alarm system, to-rye cannot be carried out without participation of cells of N. (see. Conditioned reflex ).

In experiments it is revealed that application on bark of the antiglial-ny gamma-globulin which is selectively damaging N.'s cells leads to the expressed changes of electric activity of neurons. At the same time the volume of convergence considerably decreases, up to total loss of ability to the analysis and synthesis of heterogeneous vozbuzhdeniye.

Biochemistry

Progress in studying of biochemistry of cells of N. is connected with development of methods of their allocation, among to-rykh distinguish the following: 1) method of micromanipulations, or micrurgy (see), at Krom by means of micromanipulators under control of a microscope from cuts of fabric excise N.'s cells; 2) a method of receiving the enriched fractions of cells of N. and neurons, at Krom tissue of a brain disaggregate by a transmission it through a sieve with the decreasing sizes of openings, and centrifuge the received suspension of cells in a gradient of density of sucrose and divide into fractions of cells of N. and neurons; 3) method cultures of cells and fabrics (see). However each separately taken method is not absolutely sufficient for allocation of cells of N. in pure form therefore for their more authentic biochemical characteristic use at least two of the methods stated above. The data obtained at the same time are relative and show hl. obr. qualitative distinctions in the maintenance of this or that component in different types

of N. Imeyushchiyesya biochemical, characteristics of cells of N. are received generally as a result of a research of the astrocytes and oligodendrocytes making apprx. 90% of total quantity of cells of N. in a brain. Biochemical, the characteristic of a microglia and an ependyma is developed insufficiently.

The dense rest of N. of bark and a brainstem makes apprx. 20%. Absolute value of dry weight of one glial cell depends on a type of a cell and a method of its allocation. So, the dry weight of astrocytes depending on a method of their allocation fluctuates within 500 — 1000 and 500 — 2000 mg on 1 cell whereas the dry weight of oligodendrocytes is much less — 25 — 100 pg on 1 cell.

The main part of the dense rest of cells of N. is made by high-molecular substances — lipids (see), proteins (see), nucleic acids (see), carbohydrates (see) and low-molecular substances — amino acids, nucleotides (ATP) and electrolytes (ions of sodium and potassium). The maintenance of lipids in astrocytes is about 1,5 — 2 times higher, than in neurons; they make apprx. 1/3 all dense rests.

Qualitatively the structure of lipids of cells of N. is characterized by the maintenance practically of all classes of lipids — phospholipids, galactolipids, cholesterol, fat to - t, etc. The lipidic structure of oligodendrocytes has looking alike structure of a myelin. Gangliosides are found in astrocytes and oligo dendrocytes.

Protein content in cells of N. allocated by means of various methods fluctuates per dry weight from 30 to 50%. As a part of proteins the acid proteins specific to N.'s cells are found: the acid fibrous protein of a glia (GFA-pro-tein — glia fibrillary acid protein) concentrated in astrocytes and the protein S-100 which is contained in astrocytes and oligodendrocytes. Such proteins appear in N.'s cells at early stages of their differentiation. Proteins of cells of N. differ from proteins of neurons in high content of sulphhydryl (SH) groups. Content of DNA in kernels of cells of N. approximately same, as in neurons (apprx. 6,4 pg in terms of 1 cell). In oligodendrocytes the content of RNA makes 1,8 — 2,0 pg on 1 cell, and in astrocytes it is much higher — 10 — 12 pg on 1 cell.

In N. practically all glycogen found in a brain is concentrated; its contents makes about 1 — 2% of all dry weight of cells of N.

Determination of content and distribution of low-molecular weight compounds in N.'s cells is extremely difficult. It is established that in astrocytes concentration of a number of replaceable amino acids (glutaminic to - you, a glutamine, piperidic to - you, asparaginic to - you, glycine, alanine) makes 1/3 — V8 from their concentration in a complete brain.

The N is characterized by rather high metabolic activity. Speed of oxygen consumption by N.'s cells on average makes up to 200 µmol! hour on 1 g of fresh weight of fabric. In an experiment it is shown that respiratory activity of astrocytes and oligodendrocytes is especially high when as substrate use succinate while oxygen consumption of an ependimotsitama most intensively in the presence of other substrates — glucose, pyruvate, mannose and a lactate. It is calculated that apprx. V3 of respiratory activity of a cerebral cortex of rats it is the share of N. Glycoclastic activity of cells of N. and neurons approximately the same, as well as glycoclastic activity found in cuts of a cerebral cortex (about 200 µmol at 1 o'clock on 1 g of fresh weight of fabric). Activity of oxidizing enzymes in oligodendrocytes of c. the N of page increases during myelination. Cells of an ependyma differ in high activity of oxidizing enzymes. In N. of peripheral nerves (neurolemmocytes) oxidizing enzymes are characterized by also high activity; their uneven distribution is noted: the succinatedehydrogenase of a loco

lizutsya preferential in distal departments of cells at Ranvye's interceptions; OVER - and NADF-diaphorases are distributed on cytoplasm evenly. Activity of Na, K-dependent ATP-ase in N.'s cells is higher, than in neurons. Karboangidraza is preferential localized in N.

Predpolagayut's cells that N.'s cells participate in metabolism of neurotransmitters. They possess the highly effective transport mechanism of capture of amino acids and the developed fermental systems of their catabolism. Capture by N.'s cells glutaminic to - you, piperidic to - you, taurine, glycine and asparaginic to - you are an important point in the course of an inactivation of substances mediators.

At various patol, processes in a nervous system of N. reacts change of metabolic activity. So, at tumors, coming from different types of cells of a glia (gliomas), increase in content of DNA, an intensification of its synthesis, synthesis of RNA and proteins, increase in activity of oxidizing enzymes and enzymes of phosphoric exchange is observed (ATP-ases and tia-minpirofosfataza). These changes are observed in all cells of N., but are most expressed in astrocytes. At wet brain activity of ATP-ase and a tiaminpirofosfataza increases only in astrocytes. At various forms of a gliosis the content of the acid proteins characteristic of astrocytes increases; activity of acid hydrolases at the same time increases in astrocytes and oligodendrocytes. At spasms owing to poisoning with various toxicants in N. of a spinal cord the content of RNA, proteins and various funkts, groups of proteins decreases. Consider that at epileptiform spasms protective function H. is broken, edges normal interferes with excess accumulation of potassium ions in intercellular space. At patients with parkinsonism in N. the content of RNA increases and the players of nucleotides are sharply changed. At a hyperthyroidism intensity of protein synthesis in N. decreases, and at a hypothyroidism — increases. It is noted that N.'s cells are steady against a hypoxia more than neurons, and functional shifts at this state are minimum; at the same time activity of a lactate dehydrogenase and enzymes of a pentozny cycle whereas activity of a succinatedehydrogenase and cytochrome oxydase remains high decreases.

Patomorfologiya

N.'s Cells at a row patol, processes can ambiguously react as their sensitivity to the damaging agents and time of emergence of reaction are various. Methods morfol, researches (histochemical, cytochemical, a submicroscopy) allowed to open thin disturbances in N. at various patol, processes.

N.'s reaction at various patol, states is expressed in dystrophic changes, to-rye can have reversible and irreversible character, and in reparative changes.

Reversible dystrophic changes of astrocytes. Swelling and hypostasis of shoots of the astrocytes which are among shoots of nervous cells are observed at hypostasis and brain swelling of various genesis (see. Swelled also swelling of a brain ), is more often owing to a hypoxia; process of swelling is followed by the excess maintenance of a glycogen in astrocytes, generally it is noted in the astrocytes located near the nervous cells which are characterized by dark osmiofilny cytoplasm and a karyoplasm. In vascular legs of the astrocytes contacting to a basal membrane of capillaries, granules of a glycogen meet very seldom. Development of dystrophic changes in a nervous cell and N.'s cell is interconnected: degree patol, changes of cells of N. to a great extent is defined by expressiveness of destructive changes and a possibility of reparative processes in nervous cells. Reaction of astrocytes to a lack of oxygen is explained by their metabolic features. The hypoxia causes in astrocytes decrease of the activity of a lactate dehydrogenase and enzymes of a pentozny cycle whereas activity of a succinatedehydrogenase and cytochrome oxydase remains on rather high level. Electronic microscopically acute swelling of astrocytes and their shoots is followed by emergence in their cytoplasm of small scraps of membranes, osmiofilny particles, and sometimes and large fragments of these structures that reflects the initial stages of absorption by N.'s cells of the destroyed neurons (see. Neyronofagiya ).

Fig. 10. Microdrugs of a brain at focal defeats: and — mast cells of Nissl (are specified by shooters) with an ectopia of kernels, homogeneous cytoplasm and short shoots; — a huge one-nuclear astrocyte without fibrilla and with reinforced shoots; in — a huge astrocyte with the multiple kernels located on the periphery; coloring by Snesarev's method; x 900.
Fig. 1. Microdrug of the center of a softening of a brain: shooters specified hypertrophied fibrous astrocytes; coloring by Snesarev's method; X 400. Fig. 2. Microdrug of a brain at the progressing paralysis: the field of vision is covered with hypertrophied fibrous astrocytes. Impregnation by a gold and sublimate method Ramón-and-Kakhalya; X 250. Fig. 3. Microdrug of a brain at a diabetic coma: disintegration (klazmatodendroz) shoots of astrocytes (are specified by shooters) on fragments. Impregnation by method Ramón-and-Kakhalya; X 250. Fig. 4. Microdrug of a brain: hypostasis and swelling of oligodendrocytes (are specified by shooters). Impregnation by silver by Miyagava's method — Aleksandrovskoy; x 400. Fig. 5. Microdrug of the site of a brain from an okolonekrotichesky zone: a hypertrophy of microgliocytes (are specified by shooters); X 400. Fig. 6. Microdrug of a brain: dystrophic changes of a microgliocyte (it is specified by an arrow). Impregnation by Miyagava's method — Aleksandrovskoy.

Reparative changes of astrocytes. The hypertrophy of astrocytes is characterized by uniform increase in body capacity of a cell and astrocytic shoots (tsvetn. fig. 2). If increase in a body of a cell prevails, then such astrocytes call mast cells of Nissl (fig. 10, a). Cytoplasm of these astrocytes of homogen, a kernel light with large glybka of chromatin, shoots thin. Mast cells are characteristic of a general paralysis. Hypertrophied astrocytes are observed usually near the centers of a necrosis, hemorrhages, tumors, etc.

Hypertrophied astrocytes of the huge sizes, ugly forms meet at a tuberous sclerosis (fig. 10, b). At tumors of a brain, and also regenerator processes as a result of incomplete cell fission multinuclear huge astrocytes are formed (fig. 10, c). Find the increased chromosome number in big lobular kernels of such cells. The hypertrophy of astrocytes occurs due to increase in specific intracellular structures (ribosomes, the policy, an endoplasmic reticulum, fibrilla etc.) also is followed by an intensification of protein synthesis and strengthening of RNA in cytoplasm. In kernels the strengthened accumulation of RNA is observed, average concentration of DNA and its contents increase in a kernel, activity of enzymes okislitelno - a recovery cycle amplifies. Such hypertrophy of astrocytes has compensatory character. The hypertrophy of astrocytes with formation of a significant amount of lysosomes, phagosomas, lipidic inclusions develops also owing to absorption (phagocytosis) of various decomposition products patholologically of the changed cells.

The hyperplasia of astrocytes can be focal and diffusion. The focal hyperplasia occurs near sites of destruction of a brain, around specific granulomas (a gumma, a tubercle), tsistitserok, plaques of multiple sclerosis, and also during the formation of a hem of a brain. The hyperplasia has a peculiar character at gliosis (see), to-ry develops at hron, wet brain. The hyperplasia of astrocytes at the same time is followed by strengthening of fibrillation.

The diffusion hyperplasia of astrocytes is observed in cases of widespread damages of a brain (at a general paralysis, neurosyphilis, atrophic processes of a brain).

Division of mature astrocytes happens usually amitotichesk. Mitotic activity of astrocytes is observed at a malignancy of glial tumors, napr, astrocyte (see). The astrocytes which are a part of astrocytomas can be almost not changed morphologically or not to differ from giperplazirovan-ny astrocytes. Astrocytes of the same character are noted also in other tumors — polymorphic and genetic gliomas, ganglioneuromas, astroblastomas (see. Brain, tumors ), where they can occur among cellular elements of embryonal type.

Treat irreversible dystrophic changes of astrocytes klaz-matodendroz, an amoeboid (altsgey-merovsky) glia, homogenizing metamorphoses, involute (senile) changes (tsvetn. fig. 1 — 3).

Klazmatodendroz — disintegration of shoots of astrocytes on fragments — can be observed at hypostasis and brain swelling, at intoxication which is violently proceeding inf. diseases. This state can develop very quickly, napr, at an injury of a brain.

Fig. 11. Microdrug of a brain at acute psychosis: and — cytoplasm of astrocytes (1) is homogenized, shoots are shortened and thickened, kernels (2) are hyperchromic; — granular disintegration of an astrocyte (it is specified by an arrow) with loss of borders of a cell; X 400.

The amoeboid glia described by Alzheimer (A. Alzheimer, 1910), is characterized by profound destructive changes of astrocytes that is expressed in shortening of their shoots (fig. 11, a), a lysis of fibrilla, a hyperchromatosis and wrinkling of kernels. By outward such cells remind amoebas (the name «amoeboid» a glia from here). In process of progressing of process there is a coagulation of cytoplasm and granular disintegration (fig. 11, b) to a karyopyknosis or a karyorrhexis and loss of borders of a cell. The data received at electronic microscopic examination allow to connect genesis of an amoeboid glia with excessive swelling of cytoplasm of astrocytes and their shoots. The amoeboid glia can be observed at nek-ry acute inf. diseases, injury of a brain, acute psychoses, insulin coma. Sometimes the progressing dystrophy of astrocytes proceeds with sharp reduction of cytoplasm. As a result there are almost naked large figured or puzyrkovidny kernels owing to their incomplete division or swelling. These changes meet at hepatocerebral dystrophy and a number of the encephalopathies arising owing to a liver failure. The reason of defeat of astrocytes at hepatic encephalopathies consider excess contents in an organism of endogenous ammoniac connections.

Homogenizing metamorphoses it is observed in the hypertrophied astrocytes which are localized in the sites of a brain which underwent a prelum. Cytoplasm at the same time is homogenized, the kernel atrophies. From such dead of astrocytes homogeneous formations of the extended form — so-called rozentalevsky fibers form.

Involute changes of astrocytes are noted at the progressing presenile dystrophy of a brain. In these cases there is a proliferation of astrocytes, edges in the beginning then is replaced by destructive changes with the advent of vacuoles in shoots of astrocytes; process often comes to an end with development a spongiosa of brain fabric.

In process fiziol, N.'s aging undergoes complex changes of dystrophic character: the hypertrophy of astrocytes with growth of shoots, strengthening of fibrillation, and also klazmatodendroz and granular disintegration is found. Phagocytal properties of astrocytes in relation to dystrophic to the changed neurons amplify; neurons are exposed to phagocytosis, at to-rykh integrity of a plasmolemma is broken. In this regard in many astrocytes accumulation of lysosomes and lipofuscin is observed. However astrocytes keep high reactive ability up to deep senile age; so, contents nucleinic to - t in kernels of astrocytes significantly does not change.

Reversible dystrophic and reparative changes of oligodendrocytes consist in their swelling, a hyperplasia and a hypertrophy. During the swelling the volume of cells increases (tsvetn. fig. 4), extend intracellular sine. In cytoplasm of an oligodendrocyte there is a swelling of mitochondrions and expansion of tubules of an endoplasmic reticulum. These changes quickly develop at hypostasis and brain swelling, especially traumatic genesis, at nek-ry acute inf. diseases, intoxication.

Fig. 12. Microdrug of a brain at a hyperplasia and a hypertrophy of shoots (1) and bodies of oligodendrocytes (2); impregnation by Miyagava's method — Aleksandrovskoy; X 400.

The hyperplasia and hypertrophy of oligodendrocytes (fig. 12) are the expressed reaction to nek-ry infectious diseases, intoxication of the endogenous and exogenous nature, traumatic and other local injuries of a brain. At destruction of neurons proliferating satellites — oligodendrocytes rezorbirut decomposition products. At a malarial coma from an oligodendrogliya and a microglia around zones of ring-shaped hemorrhages Dyurk's granulomas form. Oligodendrocytes actively participate in phagocytosis, especially at demyelinating processes. At the same time in them there is a full disintegration of a myelin cover, the number of ribosomes and tanks of an endoplasmic reticulum increases. Hommes and Le Blond (O. R. Not-mes, G. P. Leblond, 1967), and also N. D. Grachev (1968) in an intact brain in an oligodendrogliya was observed by mitoses. E. V. Didimova and sotr. (1974) found high percent of mitoses only at wound of a brain. Formation of the multinuclear complexes which are not divided until the end of oligodendrocytes is often observed at their hyperplasia.

Irreversible dystrophic changes of oligodendrocytes are expressed in their destruction and an atrophy. Destruction is followed by disintegration of organellas of cytoplasm (a lysis of ribosomes and the policy), accumulation of lipidic inclusions. Cells get a form of bubbles and break up. Such changes are noted in zones hron, wet brain, and also at tumors of a brain.

At an atrophy of oligodendrocytes bodies of cells and their shoots decrease, kernels shrivel. The atrophy is observed at senile age, at the progressing chorea, a side amyotrophic sclerosis. At senile age the ultrastructure of oligodendrocytes is characterized by sharp strengthening of an osmiofiliya of a kernel and cytoplasm. The majority of oligodendrocytes dystrophic are changed: contents of cytoplasm and a kernel are homogenized, organellas disappear; cells shrivel or, on the contrary, bulk up.

Ependimotsita in patol, conditions are exposed to various changes: to vacuolation, obesity, necrobiosis and necrosis.

Fig. 13. Microdrugs of a cerebral cortex at a hypertrophy (a) and an atrophy (b) of microgliocytes.
Fig. 14. Microdrug of a cerebral cortex at a diffusion hyperplasia of microgliocytes; impregnation by Miyagava's method — Aleksandrovskoy, x 250.

Reversible dystrophic and reparative changes of microgliocytes are expressed in their hypertrophy, a hyperplasia and so-called phagocytal reaction. The hypertrophy (fig. 13, a) is characterized by a thickening of bodies and shoots of cells. In cytoplasm the number of inclusions and the policy increases. The hyperplasia of a microglia happens diffusion and focal. The diffusion hyperplasia (fig. 14) can be observed at acute and hron. inf. diseases, intoxication, vascular damages of a brain. Emergence of rod forms of microgliocytes is characteristic of sharply expressed hyperplasia. The focal hyperplasia is observed near local injuries of a brain (tsvetn. fig. 5), during the formation inf. granulomas, in so-called senile plaques at senile dementia, in a molecular layer of a cerebellum in the form of a mezoglial-ny sincytium at belly and a sapropyra. Microgliocytes quickly proliferate close retrogradno the damaged neurons (at section of an axon) therefore there is a dissociation of interneuro-nalnykh bonds. Getting into cytoplasm of neurons, microgliocytes and their shoots englobe the breaking-up its particles.

Phagocytal reaction of a microglia with transformation of microgliocytes into granular spheres is most brightly shown in the period of a reparation in the centers of destruction of brain fabric. Zh. V. Solovyova, D. D. Orlovskaya (1979) found signs of phagocytal function of a microglia at embryos.

Dystrophy and an atrophy belong to irreversible dystrophic changes of microgliocytes actually. Dystrophy is characterized by wrinkling or swelling of bodies of cells, pycnosis of kernels, coarsening and fragmentation of shoots, and in more hard cases — full disintegration of cells (tsvetn. fig. 6). It is observed at heavy inf. diseases and at intoxication with the expressed hypoxia. At the atrophy of microgliocytes (fig. 13, b) which is observed at schizophrenia, presenile psychoses, at a heavy hron, intoxication and also in an extreme old age, the body capacity of a cell decreases, sharply expressed thinning of shoots, reduction of their number is noted.

the Long hypoxia developing in the predago-nalny period leads postmortem changes of a neuroglia to decrease in oxidizing and glycoclastic processes. The glycoclastic pathway of carbohydrates in the agonal period does not provide processes of resynthesis of makroergichesky phosphoric connections that leads to considerable decrease in ATP and ADF. Sharply activity of respiratory enzymes decreases (OVER - and NADF-diaphorases, succinatedehydrogenases, lactate dehydrogenases). N.'s changes after death of an organism consist in loss tinktorialny properties, swelling, fragmentation and killing. Electronic microscopically the most precursory symptom of an autolysis — swelling of shoots of astrocytes. Further there is spraying of chromatin, depression of organellas of cytoplasm of all cells of N., especially oligodendroglyocites, loss of an osmiofilnost of a microglia. In a day after death a lysis of a significant amount of cells is noted, in two days the majority of cells N. Naiboley lyses the microglia is steady against an autolysis.

See also Cell .



Bibliography: Avtsyn A. P. and Rabinovich A. Ya. O development of histiocytes of a brain («mesoglia») in a human embryo, Works Psikhiat. клиники_1st-go Mosk. medical in-that, t. 3, century 4, page 41, 1937; Aleksandrovskaya M. M. A bindweb at various psychoses, M., 1950; The B ate e of c to and y V. K. Gistogenez of a mesoglia, Owls. psikhonevrol., No. 1-2, page 60, 1932; Blinkov S. M. and Iva of N and Central Committee and y G. R. About quantity of glial cells in a brain of the person, Biophysics, t. 10, century 5, page 817, 1965; Of l e-bov R. N. and Bezruchko S. M. Exchange processes in system neuron glia at various physiological and morbid conditions of a nervous system, Zhurn, a neuropath, and psikhiat., t. 73, century 7, page 1088, 1973, bibliogr.; Dee D and m about - in and E. V., Svanidze I. K. and Ma-charashvili D. N. Features of mitotic division of macroglial cells after an injury of a cerebral cortex, Arkh. annate., gistol, and embriol., t. 67, No. 11, page 63, 1974; Lenindzher A. Biochemistry, the lane with English, M., 1976; The M and to ate and d z e A. JI. Structural organization of vegetative kernels of the central nervous system, t. 1, Tbilisi, 1968; The Multivolume guide to neurology, under the editorship of N. I. Grashchenkov, t. 1, book 1, page 222, M., 1959; The Multivolume guide to pathological anatomy, under the editorship of A. I. Strukov, t. 2, page 55, M., 1962; General physiology of a nervous system, under the editorship of P. G. Kostiuk and A. I. Roytbak, page 607, L., 1979; Peters A., Paley S. and Webster G. Ultrastructure of a nervous system, lane with English, M., 1972; P about yt-and to A. I. Neyrogliya and formation of new nervous bonds in a cerebral cortex, in book: Mechanisms of formation and a tormosheniye of conditioned reflexes, under the editorship of V.S. of Russia-is new, page 82, M., 1973; Strukov A. I. iserovv.v. Pathological anatomy, M., 1979; Functions of a neuroglia, under the editorship of, A. I. Roytbaka, Tbilisi, 1979; Sh e of l and - Hove V. N., etc. About a possible role of a neuroglia in activity of a nervous system, Usp. fiziol, sciences, t. 6, No. 3, page 90, 1975, bibliogr.; Biology of neuroglia, ed. by W. F. Windle, Springfield, 1958; Glees P. Neuere Ergebnisse auf dem Gebiet der Neurohistologie, Nissl-Substans, corticale Sinapsen, Neuroglia und intercel-lulaler Raum, Dtsch. Z. Nervenheilk., Bd 184, S. 607, 1963; Hertz L. Schousboe A. Ion and energy metabolism of the brain at the cellular level, Int. Rev. Neurobiol., v. 18, p. 141, 1975, bibliogr.; Horstmann E. Was wis-senwir iiber den intercellularen Raum im Zentralnervensystem? Wld Neurol., Bd 3, S. 112, 1962; Kuffler S. W. a. N i-c h o 1 1 s J. G. The physiology of neuroglial cells, Ergebn. Physiol., Bd 57, S. 1, 1966, Bibliogr.; Metabolic compartmenta-tion in the brain, ed. by R. Balazs a. J. E. Cremer, N. Y., 1972; N i s s 1 F. u. Alzheimer A. Histologisehe und histopathologische Arbeiten iiber die Gross-hirnrinde mit besonderer Beriicksichtigung der pathologischen Anatomie der Geistes-krankheiten, Jena, 1910; Pe.n field W. Neuroglia and microglia, in book: Special cytology, ed. by E. V. Cowdry, p. 1031, N.Y., 1928; Somjen G. G. Electro-physiology of neuroglia, Ann. Rev. Physiol., v. 37, p. 163, 1975, bibliogr.; Spiel-m e y e r W. Histopathologie des Nerven-systems, B., 1922; Watson W. E. Physiology of neuroglia, Physiol. Rev., v. 54, p. 245, 1974, bibliogr.; W e i-g e r t C. Beitrage zur Kenntnis der norma-len menschlichen Neuroglia, Frankfurt am Main, 1895; Wolff J. Die Astroglia im Gewebsverband des Gehirns, Acta neuropath. (Berl.), Bd 4, S. 33, 1968.


H. H. Bogolepov; P. B. Kazakova, V.P. Tumanov (patomorfologiya), Yu. N. Samko, A. I. Roytbak (physical.), M. G. Uzbekov (biochemical).

Яндекс.Метрика