Primary Alterations of the Genetic Apparatus
The impact of pathogenic factors on the genetic apparatus leads to fatal consequences for the cell. There are four main scenarios of primary damage:
- Mutations. Stable, irreversible changes form in the genotype.
- Activation of pathogenic genes. "Silent" or aberrant DNA segments are activated, the expression of which is normally suppressed.
- Blockade of normal expression. The synthesis of physiologically essential proteins is distorted or completely halted.
- Integration of foreign DNA. Exogenous fragments are incorporated into the genome (a classic example is viral infection).
Cascade of Matrix Process Impairments
Primary defects inevitably trigger failures in fundamental life processes. The cell loses its ability to process information correctly at all stages:
- Replication (DNA duplication before division) is disrupted.
- Transcription (RNA synthesis on a DNA template) suffers.
- Translation (direct assembly of the protein molecule) is distorted.
- Repair is suppressed (the capacity to restore damaged segments decreases).
The ultimate result is a disorder of the cell cycle: the cell loses its ability to divide and proliferate adequately, which is a direct pathway to malignancy.
Disorganization of Regulatory Systems
In addition to direct DNA damage, cellular function is impaired due to the breakdown of control systems at the receptor and post-receptor levels. The cell ceases to respond adequately to biologically active substances (BAS). This occurs via three pathways:
- Alteration in receptor number. The density of receptors on the membrane or within the cytoplasm may pathologically increase or decrease.
- Impaired sensitivity. The affinity of the receptor for its ligand is reduced or distorted.
- Breakdown of intracellular messengers. Secondary messengers and phosphorylation cascades fail to transmit signals from the receptor to effector structures.
Standard Forms of Cell Pathology
Genetic and regulatory failures lead to the development of standard pathological processes. These include:
- Dysplasia (impaired differentiation, growth, and development).
- Dystrophy / Degeneration (metabolic failure with structural alterations).
- Necrosis (cell death).
- Pathological variants of apoptosis.
- Defects in individual subcellular structures.
Cellular Dystrophies: Mechanisms of Development
Dystrophy occurs when plastic processes and metabolism are disrupted. There are four mechanisms of its development:
- Synthesis of abnormal substances (e.g., the formation of the protein-polysaccharide complex amyloid).
- Excessive transformation (overproduction of normal metabolic conversions of one compound into another, such as carbohydrates into fats).
- Decomposition (phanerosis) (breakdown of membrane protein-lipid complexes and other subcellular structures).
- Infiltration (accumulation of excess substances within the cell, such as calcium ions or low-density lipoproteins in atherogenesis).
Depending on which metabolic pathway is affected, dystrophies are classified as protein (dysproteinoses), lipid (lipidoses), carbohydrate, pigmentary (dyspigmentoses), mineral, and storage diseases (thesaurismoses).
Characteristics of Protein and Lipid Dystrophies
Protein dystrophies are accompanied by changes in the physicochemical properties of proteins, leading to the loss of their structural and enzymatic functions. This process often undergoes three sequential stages leading to necrosis: granular, hyaline-droplet, and hydropic change.
Lipid dystrophies manifest as the accumulation of lipids where they should not be, an increase in their quantity, or an alteration in their chemical composition. They are classified as primary (genetic enzymopathies, such as sphingomyelin lipidosis) and secondary (resulting from exogenous or endogenous factors: ethanol, barbiturates, cytostatics, phosphorus compounds).