42. Morphology of apoptosis: ultrastructural features. Comparative characteristics of necrosis and apoptosis.

The morphogenesis of apoptosis consists in the loss of water by the cell under the action of special selective enzyme transport systems regulating the exchange of potassium, sodium, chlorine and water ions. As a result, all organelles undergo condensation, after which the cytolemma is innvaginated in several sites, accompanied by the separation of the cytoplasm and nucleus into parts. The process ends with the formation of apoptotic bodies - fragments of the cytoplasm and the cell nucleus surrounded by a cytomembrane. Apoptotic corpuscles are phagocytized by neighboring cells, which is ensured by the special adhesive properties of the corpuscles due to the expression on the membranes of certain molecules that bind to the receptors and lectins of the membranes of surrounding cells. Apoptotic corpuscles can also be removed with the secretion of glands, lymph and blood flow.

Differences between apoptosis and necrosis:

a) prevalence: necrosis can take over the territory from a part of a cell to an entire organ, apoptosis spreads only to individual cells or groups of them.

b) apoptosis is controlled genetically (synthesis of the anti-oncogene p53 leads to activation of apoptosis), necrosis is not

c) biochemically: during apoptosis, the destruction of the nucleus occurs with the participation of special endonucleases that cleave DNA to form fragments of the same size, and hydrolytic enzymes are never activated in the cytoplasm

d) morphologically: apoptosis - condensation and marginalization of chromatin, indentation of the contours of the nucleus, formation of apoptosis bodies connected by cytoplasmic processes and their phagocytosis; necrosis - disordered decomposition of chromatin, swelling of organelles and foci of membrane destruction, cell autolysis under the action of hydrolytic enzymes

e) there is no inflammatory reaction to apoptosis, and necrosis is present.

43. Dysregulation of apoptosis in pathology, types, clinical significance. Examples of pathological processes.

The importance of apoptosis in pathology is significant, since it is observed in most pathological processes and diseases. A violation of its regulation leads to a change in tissue homeostasis due to the imbalance between cell death and proliferation.

Types:

Excessive (in viral infections),

insufficient (in hyperplastic processes,

autoimmune diseases)

incomplete (in some malignant tumors) apoptosis are isolated.

Examples of pathological processes: apoptosis is of particular importance in the development of atrophy, for example,

• in atrophy of the renal parenchyma as a result of obstruction by a ureter stone,

• in the death of cardiomyocytes in the dynamics of chronic myocardial ischemia,

• in neurodegenerative diseases, etc.

• The death of B and T lymphocytes, the breakdown of target cells during cellular immunity reactions and transplant rejection occur by apoptosis. It is stimulated by chemotherapeutic and radiation effects in malignant tumor growth.